UNIVERSITY   OF   CALIFORNIA 

ARCHITECTURAL  DEPARTMENT   LIBRARY 


CLASS 


GIFT  OF 
Mrs.   George  Beach 


From  the  collection  of  the 


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relinger 

Jjibrary 
t         P 


San  Francisco,  California 
2006 


CONCRET 


BY 

JOHN  C.  TRAUTWINE,  JR. 

'      AND 

JOHN  C.  TRAUTWINE,  3D. 

CIVIL    ENGINEERS 


FIRST  EDITION,  SECOND  THOUSAND 


REPRINTED  FROM 

TRAUTWINE'S 
CIVIL  ENGINEER'S  POCKET-BOOK 


TRAUTWINE  COMPANY 

257  S.  FOURTH  STREET 
PHILADELPHIA 

CHAPMAN  &  HALL,  LTD.  RENOUF  PUBLISHING  CO. 

LONDON  MONTREAL 

1909 

CORRECTED 
1916 


T7 


Copyright  1909  by 
JOHN  C.  TRAUTWINE,  JR. 

AND 

JOHN  C.  TRAUTWINE,  3o. 


WM.   F.    FELL  COMPANY 

ELECTROTYPER8  AND  PRINTERS 
PHILADELPHIA 


MURPHY-PARKER  CO. 

BINDERS 
PHILADELPHIA 


PREFACE. 


In  the  nineteenth  (1909)  edition,  100th  thousand,  of  our  Civil 
Engineer's  Pocket-Book,  the  most  notable  of  the  new  features  is  the 
series  of  articles  on  Concrete  (plain  and  reinforced),  including 
Cement,  Sand  and  Mortar.  Practically  all  of  this  matter  (occupy- 
ing about  200  pages),  altho  by  no  means  original,  is  entirely  new, 
so  far  as  our  publications  are  concerned.  In  compiling  it,  our 
object  has  been  to  present,  in  convenient  and  condensed  form,  the 
essentials  of  existing  knowledge  and  opinion  in  regard  to  these 
subjects. 

Special  attention  has  therefore  been  given  to  the  rules  and  results 
of  modern  practice  in  concrete  construction  ;  a  feature  which  is 
reflected  thruout  the  text  and  especially  in  the  "Selected  Results 
of  Experiment  and  Practice,"  pp  1135,  etc.,  and  in  the  "Digest of 
Specifications,"  pp  1184,  etc.  These  contain,  we  believe,  a  more 
complete  and  more  conveniently  classified  presentation  of  modern 
practice  in  concrete  than  is  to  be  found  elsewhere  in  equal  space. 
To  attain  this,  great  care  has  been  taken  jo  to  arrange  the  material 
as  to  give  maximum  density  in  the  resulting  text,  and  maximum 
convenience  for  reference. 

In  the  selection  of  "results  of  experiment  and  practice,"  we  have 
had  in  mind  not  only  the  weight  and  standing  of  the  authorities 
quoted,  but  also  the  importance  of  covering,  as  nearly  as  possible, 
the  entire  field  of  practice,  with  its  very  numerous  and  diversified 
problems. 

For  reasons  explained  on  p  1140,  it  was  found  impracticable  to 
arrange  these  results  in  satisfactory  logical  order,  and  they  are 
therefore  furnished  with  a  special  and  very  complete  table  of 
contents,  or  "Directory,"  pp  1135-1139,  arranged  in  practically 
the  same  order  as  are  the  articles  on  cement,  etc.,  pp  930,  etc.,  and 
on  concrete,  etc.,  pp  1084-1134.  It  is  believed  that,  in  connection 
with  this  ' '  Directory, ' '  the  ' '  selected  results ' '  will  be  found  a 
very  useful  feature. 

Similarly,  the  concrete  specifications  have  been  selected  from 
different  lines  of  work,  including  not  only  U.  S.  Government 


81239! 


iy  PREFACE. 

operations  and  the  building  codes  of  the  larger  cities,  hut  the  care- 
fully prepared  rules  of  consulting  engineers  and  experts  in  concrete. 
As  in  the  case  of  our  digests  of  specifications  for  trusses  and  build- 
ings, etc.,  prepared  for  our  18th  Edition  (1902),  these  digests  are 
"by  no  means  mere  quotations  from  the  originals;  but,  as  their 
name  implies,  the  result  of  careful  digesting  of  the  contents  of  the 
specifications  selected  for  the  purpose  ;  their  several  provisions 
being  carefully  studied,  in  nearly  all  cases  re- worded  or  reduced  to 
figures,  and  tabulated  in  form  convenient  for  reference,  the  whole 
being  arranged  in  such  logical  order  as  to  facilitate  reference." 

The  specifications  include  those  for  concrete  blocks  and  for 
concrete  sidewalks,  adopted  by  the  National  Association  of  Cement 
Users  at  Philadelphia,  January,  1908. 

With  these  exceptions,  and  those  of  beams  and  columns,  we 
refrain  from  extended  discussion  of  special  works  (such  as  arches, 
dams,  etc. )  in  concrete  ;  confining  ourselves,  for  the  present,  to  the 
material  itself  and  its  constituent  parts. 

Under  Cement,  the  Committee  Report  of  the  American  Society 
of  Civil  Engineers,  submitted  in  1885,  has  been  replaced  by  that  of 
the  later  Committee,  submitted  in  1903  and  amended  in  1904  and 
in  1908.  The  recommendations  of  the  Board  of  U.  S.  Engineer 
Officers,  1901,  are  retained  ;  and  those  of  the  American  Society  for 
Testing  Materials  (1904,  amended  1908)  and  of  the  Engineering 
Standards  Committee  of  Great  Britain  (1904)  are  added. 

Owing  to  the  nature  of  the  materials  involved,  the  theory  of 
concrete  design  and  construction  is  less  firmly  established  and  less 
capable  of  satisfactory  demonstration  than  that  of  other  branches 
of  engineering.  m  We  have  therefore  avoided  useless  refinement  and 
expenditure  of  space  upon  this  branch  of  the  subject,  devoting 
ourselves  chiefly  to  its  practical  side ;  but  we  have  nevertheless 
endeavored  to  state,  clearly,  succinctly,  and  in  form  convenient  for 
reference  and  use,  the  commonly  accepted  theories,  as  they  affect 
the  principal  features  of  practice. 

In  the  article  on  Cost  of  Concrete,  pp  1207-1210,  we  have  aimed 
to  give  merely  the  ranges  of  cost  to  be  expected  in  different  features 
of  concrete  work,  keeping  in  mind  those  differences  of  condition 
which  so  largely  affect  the  several  items  of  cost. 

We  have  of  course  drawn  freely  upon  the  existing  literature  of 
concrete.  In  giving  credit  for  material  so  used,  we  have  aimed  to 
err  upon  the  side  of  liberality,  not  only  as  a  matter  of  justice 
to  the  authorities  quoted,  but  also  for  the  convenience  of  those  of 


PREFACE.  V 

our  readers  who  may  wish  to  study  the  sources  of  our  information 
in  further  detail.  With  the  same  object  in  view,  we  give  these 
references  with  full  detail  as  to  volume,  page,  date,  etc. ;  and  it  is 
therefore  hoped  that  these  articles,  together  with  the  references 
under  "  Bibliography, "  may  serve,  to  some  extent,  as  an  "Index 
to  Current  Literature"  on  the  subject  of  concrete. 

For  convenience  of  reference  we  reprint  here  also,  from  The  Civil 
Engineer's  Pocket-Book,  pp  454  to  461,  remarks  on  the  general 
principles  of  the  strength  of  materials,  and,  pp  494  a  to  494  h,  on 
diagonal  stresses  in  beams. 

For  economy  of  space  we  not  only  (as  heretofore)  use  such  obvious 
abbreviations  as  cen,  diag,  hor,  vert,  cem,  agg,  cone,  etc.,  but  we 
frequently  drop  qertain  letters  which  (like  "ugh"  in  "though") 
are  as  useless  as  the  "k  "  which  our  forefathers  considered  essential 
in  "niusick,"  or  the  "u"  which  our  English  cousins  still  like  to 
use  in  ; '  honour. ' ' 

The  same  consideration  of  space  has  led  also  to  the  liberal 
use  of  symbols,  such  as  D  for  "square,"  D"  for  "square  inch," 
/  for  "per,"  >  <  >  and  <  for  "more  than,"  "less  than,"  "not 
more  than"  (equal  to,  or  less  than),  "not  less  than"  (equal  to, 
or  more  than),  respectively. 

In  connection  with  the  theory  of  reinforced  concrete  we  have 
been  forced  to  the  extensive  use  of  letters  with  subscripts,  as/s,  Ec, 
etc.,  etc.  We  have  made  special  arrangements  to  secure  the  great- 
est possible  legibility  for  these  characters,  as  well  as  in  connection 
with  the  symbols,  mentioned  above. 

In  this  reprint,  the  paging  is  that  of  the  Pocket-Book  ;  and  the 
matter  is  here  accompanied  by  the  appropriate  portions  of  the 
Table  of  Contents,  Price  List,  Business  Directory,  Bibliography 
and  Index  of  that  work. 


Our  acknowledgments  are  made  to  many  who  have  assisted  us 
in  our  labors,  notably  to  Professors  A.  W.  French  and  L.  J.  Johnson, 
and  to  Messrs.  J.  Y.  Wheatley  and  Wm.  H.  Balch. 

JOHN  C.  TKAUTWINE,  JR., 
JOHN  C.  TEAUTWINE,  3D. 
PHILADELPHIA,  September,  1909. 


CONTENTS. 


In  this  reprint,  the  paging  is  that  of 
Tbe  Civil  Engineer's  Pocket-Book. 

See  Index. 


STRENGTH  OF  MATE- 


PAGE 

General  Principles. 

Stress  and  Stretch  ...........  454 

Elastic  Modulus  .............  456 

Elastic  Limit  ................  459 

Elastic  Ratio  ................  459 

Yield  Point  .................  460 

Resilience  ..................  460 

Suddenly  Applied  Loads  ......  461 


Transverse  Strength. 

Diagonal  Stresses 494o 

Horizontal  and  Vertical  Shear  494c 

Maximum  Unit  Stresses 494e 

Moments  in  Continue  us  Beams  4940 


CEMENT  MORTAR. 

Cement. 

Materials 930 

Manufacture 931 

Natural  and  Portland 931 

Puzzolana 932 

Silica  Cement 932 

Other  Cements 933 

Composition 933 

Properties 934 

Packages 935 

Age 935 

Testing 936 

Specifications 
Requirements 

U  S  Engr  Officers 937 

Am  Soc  Test  Materials  .  .  .  940 
Engng  Standds  Comm  of 

Gt  Brit 940 

Tests 

Am  Soc  Civ  Engrs 942 


Sand. 

Composition 946 

Sizes  of  Grains 946 

Density 947a 

Other  Properties 947c 


Mortar. 

Constituents 947d 

Amount  Required  in  Masonry . 


Cement  '  

.947d 

Sand  

947e 

947e 

Lime     .                             .    .    .  . 

.947/ 

Consistency  '.  " 

.947/ 

Setting  and  Hardening  
Soundness  .... 

.947/ 
947/1 

Strength  
Finish        .                 .... 

.947* 
947? 

Behavior  in  W'ater  

.947Jfc 

CONCRETE. 

Aggregates 1084 

Size 1084 

Density 1084 

Cyclopean 1085 

Constituents 1086 

Advantages 1086 

Proportions 1086 

Materials  Required 1087 

Voids 1088 

Density 1089 

Consistency 1090 

Handling  and  Mixing 1090 

Handling  Ingredients 1090 

Mixing 1092 

Mixers 1092 

Placing 1093 

Forms.  . 1094 

For  Buildings 1095 

Lumber  for — 1097 

Strength 1098 

Details 1098 

Adhesion 1099 

Removal 1099 

Joints 1099 

Ramming 1100 

Placing  under  Water 1100 

Surface  Finish 1102 

Properties 1103 

Weight - 1103 

Permeability 1103 

Elastic  Modulus 1106 

Strength 1106 

Setting 1106 

Effects  of  Heat  and  Cold 1107 


VI 


CONTENTS. 


Vll 


Protection  .  . 

PAGE 

1107 

Placing  etc  

PAGE 
1189 

Expansion  

1108 

Joints  

..1190 

1108 

Under  Water. 

.  .1190 

Tests  in  Place 

1109 

Rain 

1191 

Frost  .  . 

1191 

Moistening  

.  .1191 

Reinforced  Concrete 

. 

Removal  of  Forms  

.  .1191 

Expansion,  Contraction,  etc  .  . 
Adhesion  

1110 
1111 

Finish,  Waterproofing,  etc.  .  . 
Artificial  Stone  

..1192 
1193 

1112 

Strength. 

1193 

Hooped  

1113 
1115 

Permissible  Loads  
Elastic  Modulus.  .    . 

..1193 
1194 

Theory  
Tee  Sections.    .  . 

1115 
1122 

Safety  Factors  
Reinforcement.  .  . 

.  .1194 
1194 

Shear 

1123 

Permit 

1196 

Reinforcement  

1124 

Clearance  

1196 

Unit  —  

1125 

Columns  

.  .1197 

Diagonal  Stresses  

1125 
1126 

Beams  
Slabs 

.  .1198 
1199 

Continuous  Beams  

1126 

Continuity  

1200 

Methods 

1127 

Tests 

1200 

Bar  
Web                          * 

1128 
1132 

Sidewalks  
Blocks.  .  . 

.  .1201 
1203 

Trussed  
With  Structural  Shapes 

1133 
1133 

Column  

1134 

Cost 

Materials  

1207 

Experiments. 

Directory  
Results 

1135 
1140 

Transportation  
Storage  
Mixing  and  Placing  
Forms  

.  .1208 
.  .1208 
..1208 
1209 

Miscellaneous 

1210 

Specifications. 

Alphabetical  List  

1184 

Total  

.  .1210 

Classified  List  
Contents  

1185 
1185 
1186 

PRICE  LIST 

1301 

Sand 

1186 

Aggregate  
Consistency  

1186 
1187 

BUSINESS  DIRECTORY.. 

.  .  1307 

Mixing  

1188 

Forms.  .  . 

.1189 

INDEX. 

NOTICE. 

The  following  pages  are  selected 
from  those  of  The  Civil  Engineer's 
Pocket-Book,  and  they  are  numbered 
similarly  with  the  corresponding 
pages  in  that  book. 


IX 


>  •  if* :  2 

•  «» 

454  STRENGTH   OF    MATERIALS. 


STRENGTH  OF  MATEEIALS. 


GENERAL  PRINCIPLES. 

Stress. 

1.  Stress  occurs  when  forces  act  upon  a  body  in  such  a  way  that  its 
particles  tend  to  move  simultaneously  with  different  velocities  or  in  differ- 
ent directions;  to  do  which,  the  particles  must  change  their  relative  posi- 
tions.    This  occurs,  for  instance,  when  a  body  is  so  placed  as  to  oppose  the 
relative  motion  of  two  other  bodies;  as  when  a  block  is  placed  between  a 
weight  and  a  hor  table.     Here  the  two  bodies  (the  wt  and  the  table)  tend  to 
come  closer  together;  but  they  cannot  do  so  without  distortion  of  the  in- 
tervening block;  and  such  distortion  is  resisted  by  internal  forces,  act- 
ing betw  the  particles  of  the  block  and  tending  to  keep  those  particles  in 
their  original  relative  positions.     The  action  of  these  internal  forces  is  called 
stress.* 

2.  Similarly,  if  a  body  be  suspended  by  a  long  chord,  and  if  we  push  or 
pull  the  body  to  one  side,  the  particles,  on  the  side  acted  upon,  will   first 
tend  to  move,  and  the  transmission  of  this  tendency  to  the  remaining  par- 
ticles causes  stress  within  the  body. 

3.  For  internal  equilibrium,  the  internal  stresses  must  balance 
the    external    forces.     Hence,  it  is  not  unusual   to  apply  the  term, 
"stress,"  indifferently  to  either. 

4.  Let  the  two  forces,  a  and  b,  Figs  A,  B,  acting  upon  the  body,  o,  meet 
at  an  angle,  a  o  b.     Then  the  two  equal  and  opposite  components,  a"  o 
and  b"  o,  cause  compressive  or  tensile  stress  in  the  body,  o,  as  in  H  1;  while 
the  other  two  components,  a'  o  and  b'  o,  unite  to  fprm  the  resultant,  c  o, 
which,  unless  balanced  by  other  forces,  moves  the  body,  o,  in  its  own  direc- 
tion, causing,  as  in  H  2,  another  comp  stress,  Fig  A,  or  tensile  stress,  Fig  B. 


Fig.  B. 

5.  Upon  any  plane  within  a  body,  a  force  may  act  (1)  normally, 
(2)  taiigentially,  or  (3)  obliquely.     If  it  act  obliquely,  it  may  be 
resolved  into  two  components  (see  Statics,  H  65,  p  372),  one  acting  normally 
and  the  other  tangentially,  upon  the  plane. 

6.  Consider  the  two  portions  into  which  the  body  is  divided  by  such  a 
plane,     Then  (1)  forces,  acting  normally  upon  the  plane,  produce  ten- 
sion (or  compression)  in  the  plane,  tending  to  separate  the  two  por- 
tions (or  to  push  them  closer  together);  and  (2)  forces,  acting  tangentially 
upon  the    plane,  produce  shear  (or  torsion)  in  the  plane,  tending  to 
slide  the  two  portions  one  past  the  other  in  a  straight  line  (or  with  a  twisting 
motion).     Torsion  occurs  in  planes  betw  and  parallel  to  two  con- 
trary couples,  as  in  cross  sections  of  a  hand-brake  axle  when  the  brake 
is  applied. 

7.  Thus,  if  an  iron  bar  be  pulled  (or  pushed)  lengthwise,  its  cross  sections 
sustain  normal  tension  (or  compression).     If  it  be  sheared  across  (or  twisted), 
the  cross  sections,  between  and  parallel  to  the  two  shearing  (or  twisting) 
forces,  sustain  shearing  (or  torsional)  stress. 

8.  At  any  point,  in  the  circular  path  of  a  torsional  stress,  we  may  consider 
the  tangents  to  the  path  as  representing  shearing  forces.     Torsion  is 

*  In  every-day  language,  and  often  in  the  writings  of  engineers,  this  action 
of  the  internal  forces,  or  the  external  force  causing  it,  is  called  "strain"; 
but  scientists  apply  the  word  "  strain  "  to  the  deformation  occurring  under 
stress.  See  "stretch,"  HI  H  etc. 


GENERAL   PRINCIPLES. 


455 


therefore  merely.a  shearing  stress  in  which  the  direction  changes  at  each 
point. 

9.  Transverse  stress.     In  Fig  124,  p  438,  the  two  equal  and  parallel 
forces,  W  and  R,  in  opposite  directions,  cause  a  tangential  or  shearing  stress, 

.  =  W  =  R,  in  the  vertical  planes  lying  between  their  lines  of  action;  but 
W  and  R,  as  a  couple,  have  a  moment,  which,  for  equilibrium,  must  be  re- 
sisted by  the  equal  and  opposite  moment  of  another  couple,  as  C  and  T; 
and  the  opposition  of  these  two  couples  causes  normal  (comp  and  tensile) 
stresses  in  the  same  vert  planes  parallel  to  and  betw  W  and  R. 

10.  The  ultimate  tendency  of  any  opposing  external  forces  is  to  fracture 
the  body  by  increasing  the  distances  between  its  particles.     Even  under 
compressive  stress,  rupture  can  occur  only  by  separation  of  particles. 

Stretch. 

11.  When  the  internal  stresses  and  the  external  forces  are  in  equilibrium, 
no  distortion   takes   place;  but,    at   the   instant   when   opposing   external 
forces  are  first  applied  to  a  body,  the  internal  stresses  are  not  yet  developed, 
and  distortion  begins,  under  the  unopposed  action  of  the  external  forces. 
See  1111  35  etc.     But  the  stresses  are  brought  into  action  by  the  distortion, 
and  they  increase  with  it;  and,  if  the  external  force  is  not  increased  beyond 
the  elastic  limit  (1J  26)  the  stresses  finally  equal  the  external  forces,  and 
prevent  further  distortion. 

Strctvh.    1OOO  e  =  1OOO  l/L 

100  150  200  250 


1.0  1.5  2.0 

Stretch,    JOOO  e  —  1OOO  l/L 

Fig.  C. 

Behavior  under  Normal  Stresses. 

12.  Fig  €  represents  the  behavior  of  a  typical  material  (mild 
steel)  under  tension.  From  0  to  A,  i.e.,  under  stresses  up  to  the  elas- 
tic limit  (If  26),  say  34,000  Ibs  per  sq  inch,  the  stretch  progresses  propor- 
tionally with  the  stress,  as  indicated  by  the  straight  line,  0  A.  (The  earlier 
portions  of  the  process  are  represented,  in  the  lower  diagram,  to  a  scale  of 
stretch  100  times  as  great  as  that  of  the  upper  diagram. 1  After  passing 
the  point  A,  the  stretch  increases  faster  than  the  stress;  and,  betw  B  and  B', 
the  stretch  (in  iron  and  steel)  increases  with  little  or  no  increase  of  stress,  or 
even  under  a  slightly  diminishing  stress.*  B  is  called  the  yield  point. 
See  U  31.  The  scale  of  the  lower  diagram  does  not  extend  to  B'.  Beyond 
B'  (upper  diagram),  the  stretch  increases  much  less  rapidly  than  betw  B 


*See  tH  16,  17 


30 


456 


STRENGTH   OF   MATERIALS. 


and  B',  and  remains,  for  a  time,  nearly  proportional  to  the. stress*  (though 
much  greater,  relatively  to  stretch,  than  in  0  A);  but  the  stretch  now  pro- 
ceeds faster  and  faster,  and  in  increasing  ratio  with  the  stress,  until  the 
stress  reaches  its  maximum  or  ultimate  value  (say  70,000  Ibs  per  sq  inch) 
at  C.  At  C,  the  stretch  is  increasing  without  increase  of  stress  (diagram 
horizontal);  and,  beyond  C,  the  stretch  continues  increasing  altho  the  stress 
is  diminishing,  until,  finally,  at  D,  rupture  occurs. 

13.  If,  after  passing  the  elastic  limit,  the  bar  is  relieved  from  stress,  as 
at  F,  Fig  C,  lower  diagram,  its  recovery  is  incomplete,  the  length  remaining 
somewhat  greater  than  in  its  original  unstressed  condition.     The  permanent 
increase,  0  F',  is  called   the  permanent  set,  or  simply  the  set.     The 
line  F  F'  is,  in  general,  approx  parallel  to  the  line,  0  A,  of  elastic  stretch. 
W  hen  the  same  stress  is  again  applied,  the  stretch  is  greater  than  before,  by 
a  small  amount  represented  by  F  F". 

14.  When  the  stress  is  within    the   elastic   limit   (If   26),  the 
recovery,  upon  release  from  stress,  is  so  nearly  complete  that  the  per- 
manent set  cannot  be  indicated  in  our  Figs.     (U  28.) 

15.  Under  tension,  the  sec  area  is  diminished,  and,  under  compression 
increased.     In  ductile  materials,  under  tension,  the  reduction  of  sec  area  is 
very  marked,  especially  along  a  relatively  short  portion  of  the  length,  usually 
near  the  middle  of  said  length;  and  fracture  occurs  normally  at  the  point 
of  maximum  reduction. 

16.  In  Fig  C,  both  diagrams,  and,  in  Fig  D,  the  solid  curves,  represent 
the  nominal  unit  stresses,  or  those  usually  stated.     These  are  found 
by  dividing  the  total  stresses,  respectively,  by  the  original  section  area,  as 
in  If  18. 

17.  The  dotted  curves,  Fig  D,  represent  the  actual  unit  stresses, 
found  by  dividing  the  total  stresses,  respectively,  by  the  actual  section  area, 
as  diminished  or  increased  by  stress.     Under  tension,  the  actual  unit  stresses 
are  of  course  greater,  and,  under  comp,  less  than  the  corresponding  nominal 
unit  stresses. 


Negative  stretch 


Stretch 


li 


Fig.  D. 
Elastic  Modulus.    Fig.  C. 

18.  Let  P  =  the  load  (one  of  the  two  equal  and  opposite  external  forces) 
acting  at  one  end  of  a  bar  and  in  line  with  the  axis  of  the  bar;  and  let  a  = 
the  original*  cross-section  area,  or  section  area,  of  the  bar,  normal  to 
its  axis.  Then,  s,  =  P  I  a,  is  the  normal  stress  per  unit  of  area,  or  stress 
intensity,  or  normal  unit  stress,  in  the  bar.  We  assume  that,  so  long  as 
the  external  force  acts  axially,  P  is  uniformly  distributed  over  a,  altho  this 
is  seldom  strictly  the  case  in  practice. 

*See  HH  16,  17 


GENERAL   PRINCIPLES.  457 

19.  Let  L  =  the  original  length  of  the  bar,  or  of  some  designated  portion 
of  that  length,  and  I  =  the  stretch  *  which  takes  place,  in  the  length,  L, 
under  the  action  of  a  given  unit  stress,  s.     Then,  e,  =  I  /  L,  is  the  stretch 
per  unit  of  length,  or  unit  stretch,*  corresponding  to  the  unit  stress,  s. 

20.  In  many  materials,  the  unit  stress,  s,  and  the  unit  stretch,  e,  at  first 
increase  proportionally,  the  ratio,  s/e,  or  unit  stress  -;-  unit  stretch,  remain- 
ing practically   constant.     This   ratio  is  called  the  elastic  modulus, 
and  is  designated  by  E ;  or 

Elastic  modulus  =  E  =  s/e  =-=  unit  stress  -5-  unit  stretch. 

2O  a.  The  elastic  modulus  is  thus  proportional  to  the  tangent 

of  the  angle,  X  0  A ,  Fig  C,  the  proportion  depending  upon  the  scales  adopted . 

2O  b.  The  elastic  modulus,  E,  increases  with  the  unit  stress  reqd  to  pro- 
duce a  given  unit  stretch.  Hence  E  is  a  measure  of  the  stiffness  of  a  body, 
i.e.,  of  its  ability  to  resist  change  of  shape.  ".Stiffness  modulus" 
would  have  been  a  better  name. 

2O  c.  If  equal  additions  of  stress  could  indefinitely  continue  producing 
equal  additional  stretches  in  a  bar,  beyond  as  well  as  within  the  elastic 
limit  (H  26),  then  a  stress,  equal  to  the  elastic  modulus,  would  double  the 
length  of  a  bar  when  applied  to  it  in  tension,  or  would  shorten  it  to  zero  in 
compression. 

2O  d.  For  example,  within  the  elastic  limit,  a  one-inch  square  bar  ot 
rolled  steel  will  stretch  or  shorten,  on  an  average,  about  Q  of  its  length 

under  each  additional  load  of  1000  Ibs.  If  it  could  stretch  or  shorten  in- 
definitely at  the  rate  of  of  its  original  length  for  each  1000  Ibs.  of 

added  load,  then  30,000  times  1000  Ibs.,  or  30,000,000  Ibs.,  (which  is  about 
the  average  modulus  of  elasticity  for  such  bars)  could  either  stretch  the  bar 
to  double  its  length  or  reduce  it  to  zero. 

2O  e.  If  equal  infinitesimal  stresses,  applied  to  a  bar,  could  indefinitely 
produce  stretches,  each  bearing  a  constant  ratio  to  the  increased  length  oi  the 
bar,  if  in  tension;  or  to  the  diminished  length,  if  in  compression;  then  the 
same  load  which  would  double  the  original  length  of  the  bar,  if  applied  in 
tension,  would  reduce  it  to  half  its  original  length,  if  applied  in  compression. 

*We  regard  shortening,  under  compression,  as  negative  stretch. 


458  STRENGTlf   OF   MATERIALS. 

21.  In  a  prismatic    bar,  under  longitudinal   tension   or 
compression,  let 

W  =  the  total  load  ; 
a  =  the  cross  section  area  ; 

a  =    —  =  the  unit  stress  =  the  stress  per  unit  of  area ; 
a 

L  =   the  original  length  ; 

I  =  the  stretch  *  ; 

e  =  if  L  =  the  unit  stretch  *  =  the  stretch  *  per  unit  of  original  length  ; 
E  =  the  elastic  modulus  of  the  material ; 

r  =  E  a  =  a  measure  of  the  resistance  of  the  bar. 
Then 


Tot  al  load                 — 

W  — 

a 
E  a 

I 

•     (2) 

W 

'  L 
=   E  e 

.  (3) 

Total  stretch*       — 

1    — 

a 
W 

L 

a 

E'" 
L 

(5) 

1    ii  if    vt  !•<>!  <-ll  * 

I 

E"" 

W             8 

(6) 

22.  In  a  beam,  supported  at,  both  ends  and  loaded  at  the  center,  let 
L  =  length         of  clear  span  of  beam  ; 

w  =  weight  "  "  "  "  "  ; 
A  =  deflection  .....  '  "  "  ; 
b  =  breadth  of  cross  section  of  beam  ; 

d  =  depth  .....  '     ; 

/  =  moment  of  inertia    "       "  "       "         "     . 

Then 

F  =    (W  +  5/8  w}  L3 
'48  A  / 

b  d  3 
If  the  beam  is  rectangular,  /  =    y^-        (p  469),  and 

_  12  (W  +  5/8  w)  L*   _  (W  +  5/8  w}L* 

48  A  b  <*>  ,    4  A  frd3 

For  beams,  see  also  pp  480-481. 

23.  Reciprocal  of  elastic  modulus.    The>lastic  modulus,  = 

'  mc^cates  t^ie  8tre88  required  to  produce  a  certain  distortion. 


Its  reciprocal,  =  Umt  stretch    Sh0ws  to  what  extent  a  bar  etc  of  a 
unit  stress 


therefore,  a  relatively  great  distortion  must  take  place  before  a  given  fiber 
stress  (such  as  the  maximum  safe  fiber  stress)  can  be  brought  into  action. 
Thus,  in  the  case  of  a  wharf,  supported  by  long  timber  piles,  the  piles  may 
submit  to  so  great  a  lateral  deflection  as  to  give  the  load,  resting  upon  them, 
a  dangerously  great  horizontal  leverage,  and  thus  a  dangerous  overturning 
moment. 

*  Compression  is  regarded  as  negative  stretch. 


GENERAL   PRINCIPLES.  459 

24.  Variable    elastic    modulus.      Fig  11,  Concrete  experiments 
81a  p  1172,  shows  an  example  (in   both  tension  and  compression)  of  a 
material    in  which   the   elastic  modulus,  E,  is   constantly  changing;    the 
stretches,  from  the  first,  increasing  faster  than  the  stresses. 

25.  Even  in  the  case  of  ductile  materials,  the  stretches,  produced  by 
stresses  within  the  elastic  limit  (If  26),  are  so  small  and  so  irregular  that  a 
satisfactory  average  value  of  the  elastic  modulus  can  be  arrived  at  only  by 
comparing  the  results  of  many  experiments.     In  the  case  of  brittle  materials, 
where  scarcely  any  perceptible  stretch  takes  place  before  rupture,  the  deter- 
mination of  the  elastic  modulus  is  very  uncertain. 

Elastic  Limit. 

26.  The  stress,  0  A,  Fig  C,  beyond  which  the  stretches  in  any  body 
increase  perceptibly  faster  than  the  stresses,  is  called  its  elastic  limit, 
or  limit  of  elasticity.     Owing  to  the  irregularity  in  the  behavior  of  different 
specimens  of  the  same  material,  and  to  the  extreme  smallness  of  the  distor- 
tions caused  in  most  materials  by  moderate  loads,  and  because  we  often 
cannot  decide  just  when  the  stretch  begins  to  increase  fastei4  than  the  load, 
the  elastic  limit  is  seldom,  if  ever,  determinable  with  exactness  and  certainty.* 
But  by  means  of  a  large  number  of  experiments  upon  a  given  material  we 
may  obtain  useful  average  or  minimum  values  for  it,  and  should  in  all  cases 
of  practice  keep  the  stresses  well  within  such  values;  since,  if  the  elastic 
limit  be  exceeded  (through  miscalculation,  or  through  subsequent  increase 
in  the  stress  or  decrease  in  the  strength  of  the  material)  the  structure 
rapidly  fails.     The  table,  p  460,  gives  approximate  average  elastic  limits 
for  a  few  materials.     The  elastic  limit,  as  here  defined,  is  sometimes  called 
the  "  true  "  elastic  limit.     Compare  If  31. 

27.  Brittle  materials,  such  as  stones,  cements,  bricks,  etc.,  can  scarcely 
be  said  to  have  an  elastic  limit;  or,  if  they  have,  it  is  almost  impossible  to 
determine  it;  since  rupture,  in  such  bodies,  takes  place  before  any  stretch 
can  be  satisfactorily  measured. 

28.  A  small  permanent  "set"  (stretch)  probably  takes  place  in  all 
cases  of  stress  even  under  very  moderate  loads;  but  ordinarily  it  first  be- 
comes noticeable  at  about  the  time  when  the  elastic  limit  is  exceeded. 
The  elastic  limit  is  sometimes  defined  as  that  stress  at  which 
the  first  marked  permanent  set  appears. 

29.  The  elastic  ratio  of  a  material  is  the  quotient, 
It  is  usually  expressed  as  a  decimal  fraction. 

The  permissible  working  load  of  a  material  should  be  determined  by  its 
elastic  limit  rather  than  by  its  ultimate  strength.     Hence,  other  things 
being  equal,  a  high  elastic  ratio  is  in  general  a  desirable  qualification;  but, 
on  the  other  hand,  it  is  possible,  by  modifying  the  process  of  manufacture, 
to  obtain  material  of  high  elastic  ratio,  but  deficient  in  "body"  or  in  resil- 
ience —  i.  e.,  in  capacity  to  resist  the  effect  of  blows  or  shocks,  or  of  sudden 
application  or  fluctuation  of  stress.     See  If  34;  also  111(35  etc. 

In  the  manufacture  of  steel,  the  elastic  ratio  is  increased  by  increasing  the 
reduction  of  area  in  hammering  or  rolling,  and  the  rate  of  increase  of  elastic 
ratio  with  reduction  of  area  increases  rapidly  as  the  reduction  becomes  very 
great.     Kirkaldy  found  t 

for  steel  plates    1  inch  thick,  mean  elastic  ratio  =  0.53 
.....  '      H      "         "         "         "  "      =  0.53 

......      V*      "         "         "         "  "      =  0.54 

"      M      "         "         "         "  "      =  0.61 


*The  U.  S.  Board  appointed  to  test  Iron,  Steel,  &c.,  found  a  variation  of 
nearly  4000  Ibs.  per  square  inch  in  the  elastic  limit  of  bars  of  one  make  of 
rolled  iron,  prepared  with  great  care  and  having  very  uniform  tensile  strength; 
and,  in  another  very  carefully  made  iron,  a  difference  of  over  30  per  cent. 
between  two  bars  of  the  same  size.  Report,  1881,  Vol.  1,  p.  31. 

t  Annual  Report  of  the  Secretary  of  the  Navy,  Washington,  1885,  Vol.  I, 
p.  499;  and  Merchant  Shipping  Experiments  on  Steel,  Parliamentary  Paper, 
C.  2897,  London,  1881. 


C2 


460 


STRENGTH   OF   MATERIALS. 


3O.  Elastic  Moduli  and  Elastic  Limits.    Approximate  averages,  t 
E  =  elastic  modulus,  in  millions  of  pounds  per  square  inch  ; 
I  =  stretch  or  compression,  in  ins,  in  a  length  of  10  feet,  under 

a  load  of  1000  pounds  per  square  inch. 
=  (10  X  12  X  1,000)  -*-  (1.000,000  E) ; 
*r  =  stress  at  elastic  limit,  in  thousands  of  pounds  per  square  inch. 


m 

I 

*e 

Metals. 

10  to  30 

0  012  to  0.004 

4  to   8 

*'         "    ordinarily       .  ...            

12  to  15 

0.010-  to  0.008 

6  to    7 

27  to  31 

0.004 

20  to  40 

Steel  structural*                 

"  to  " 

34  to  38 

8  to  10 

0  015  to  0.012 

5  to    7 

**      wire           .        

12  to  16 

0.010  to  0.007 

14  to  18 

10  to  14 

0.012  to  0.009 

6  to    7 

10  to  14 

0.012  to  0.009 

8  to  12 

Lead 

0  8  to  10 

0  150  to  0.120 

1  to    1.2 

Tin   cast                      

6  to    7 

0.020  to  0.017 

1.4  to    1.6 

13  to  15 

0.009  to  0.008 

14  to  15 

Stones  etc  f                     

4  to    8 

0.030  to  0.015 

1  to    2 

0  5  to    2 

0.240  to  0.060 

Art.  4  (h) 

wSdjT.1  .""..:::  """". 

1.5  to    2 

0.080  to  0.060 

5  to    7 

31.  Yield  point.    Commercial,  Relative  or  Apparent  Elas- 
tic Limit.    In  testing  specimens  of  iron  and  steel,  it  is  commonly  found  that, 
at  a  stress  slightly  exceeding  the  true  elastic  limit  (^26),  the  stretch  begin! 
to  increase  without  further  increase  of  load.    This  point  is  usually  called  "the 
yield  point,"  or  "  the  elastic  limit"  in  commercial  testing.    The  French  Com- 
mission on   Methods  of  Testing  the  Materials  of  Construction   called  it  the 
"  apparent  elastic  limit."     The  late  Prof.  J.  B.  Johnson  ("  The  Materials  of  Con- 
struction," New  York,  John  Wiley  &  Sons,  1906,  p.  19)  applied  the  term,  "  rela- 
tive or  apparent  elastic  limit"  to  that  point  on  the  stress  diagram  at  which  the 
rate  of  deformation  is  50  per  cent,  greater  than  at  points  below  the  true  elastic 
limit. 

Resilience. 

32.  The  resilience  of  a  bar,  under  a  stress,  s,  is  the  work  done,  upon 
the  bar,  in  producing  that  stress,  or,  theoretically,  the  work  which  the  bar 
will  do,  in  regaining  its  original  shape,  when  relieved  from  stress.     Usually 
we  are  concerned  with  the  elastic  resilience,  or  that  corresponding  to 
the  stress,  »e  at  the  elastic  limit. 

33.  Let 

se    =  the  unit  stress  at  the  elastic  limit ; 
a     =  the  section  area  of  the  bar  ; 
Pg  =  a  se  =  the  load  corresponding  to  se  ; 
L    =  the  original  length  of  the  bar  ; 
I      =  its  stretch,  at  the  elastic  limit ; 
E    =  the  elastic  modulus. 


*In  rolled  iron  and  steel,  the  elastic  modulus  is  remarkably  constant  for  all 
grades.  In  wrought  iron,  the  elastic  limit  depends  chiefly  upon  the  degree  of 
reduction  of  cross  section  in  rolling;  the  smaller  sizes  having  the  higher  elastic 
limit.  In  steel,  this  effect  is  less  marked. 

t  See  UH  25,  26. 

Jin  wood,  "the  extreme  fiber  stress  at  the  true  elastic  limit  (*[f  26)  of  a  beam 
Is  practically  identical  with  the  compressive  stress  endwise  of  the  material," 
table,  p.  958.  See  discussion  by  S.  T.  Neely,  in  "Timber  Physics,"  1889  to  1898, 
by  Filibert  Roth,  House  Document  No.  181,  55th  Congress,  3d  Session,  Wash- 
ington, 1899,  p.  374. 


GENERAL   PRINCIPLES.  461 

The  work  has  been  done  by  the  mean  load,  Pe/2  =  a  se/2,  acting  thru 
the  dist,  I  =  L  se/E.     Hence, 

Resilience  =  K  =  Pe  1/2  =  a  se  L  se  /2  E  =  (sJ/2  E)  a  L. 

34.  Here  s//2  E  is  the 

resilience  modulus   =   resilience  of  a  bar  of  unit  section  area  and 

unit  Igth. 

The  resilience  modulus  of  a  material  is  a  measure  of  its  capacity  for  re- 
sisting shocks  or  blows. 

Suddenly  applied  loads. 

35.  Let  a  body,  of  weight,  W,  be  suspended  by  a  string,  and  let  it  just 
touch  the  scale-pan  of  a  spring  balance,  without  depressing  it.     Now  let 
the  string  be  cut  with  a  pair  of  scissors. 

36.  At  the  moment  of  cutting,  the  spring  has  not  been  stretched;  its 
resisting  stress,  S,  is  therefore  zero,  and  the  net  or  resultant  downward  force, 
acting  upon  the  body,  is  F  =  W  —  S  =  W  —  0  =  W. 

37.  Under  the  action  of  this  force,  the  spring  stretches,  and  S  increases 
proportionally  with  the  stretch.     Hence  (W  remaining  constant)  the  re- 
sultant downward  or  accelerating  force,  F,  acting  upon  the  body,  decreases 
until  S   =   W,  when  F   =   W  —  S   =    W  —  W   =  0. 

38.  The  body,  having  thus  far  been  constantly  accelerated,  (by  a  dimin- 
ishing force,  F),  has  constantly  increased  its  velocity.     Let  h   =   the  height 
thru  which  it  has  now  fallen,  and  let  x  be  the  point  reached,  at  the  end  of  h. 

39.  Beyond  x  (W  remaining  constant,  while  S  continues  to  increase), 
the  moving  body  is  acted  upon  by  a  constantly  increasing,  retarding  up- 
ward force,  —  F    =    W  —  S,  which  brings  it  to  rest  at  a  second  point,  z, 
at  the  end  of  a  second  distance    =   h.     Its  total  fall  is  therefore  2  h. 

40.  Let  S  max    =    the  max  value  of  S,  or  that  at  the  end,  z,  of  the  fall, 
2  h.     Then,  since  S  has  increased  proportionally  with  h,  its  mean  value, 
during  the  fall,  2  h,  was  S  max/2;    and  the  work  done,  during  the  entire 
fall,  2  h,  was  2  W  h  =    (S  max/2)   2  h   =   S  max    X   h.     Hence, 

S  max  =  2  W. 

41.  At  the  end,  z,  of  the  fall,  2  h,  the  body,  having  come  to  rest,  is  acted 
upon  by  an  upward  force,  — F  =  W  —  S  max  =  W  —  2W  =   — W;    and 
(neglecting  friction)  the  same  performance  is  now  repeated,  but  in  the  up- 
ward direction,  and  so  on  indefinitely. 

42.  But    losses  of  energy,  due  to  air  resistance   and  to  internal 
friction,  render  each  oscillation  less  than  its  theoretical  value  ;  and  the  body 
therefore  finally  comes  to  rest  at  the  point,  x,  midway  of  the  fall,  2  h. 

43.  Thus  (If  40),  within  the  elastic  limit,  a  load,  suddenly  applied 
(tho  without  shock)  produces  temporarily  a  stretch  nearly  equal 
to  twice  that  which  it  could  produce  if  applied  gradually ; 
i.e.,  twice  that  which  it  can  maintain  after  it  comes  to  rest;  and  develops 
temporarily,  in  the  stretched  body,  a  resisting  stress  =  twice  the 
load. 

44.  If  the  load  be  added    in  small  instalments,  each  ap- 
plied suddenly,  then  each  instalment  produces  a  small  temporary  stretch, 
and  afterward  maintains  a  stretch  half  as  great.     Under  the  fast  small 
instalment  of  load,  the  spring  stretches  temporarily  to  a  length  greater 
than  that  which  the  total  load  can  maintain,  by  an  amount  equal  to  half  the 
small  temporary  stretch  produced  by  the  sudden  application  of  the  last 
small  instalment. 


DIAGONAL   STRESSES   IN    BEAMS. 


494  a 


DIAGONAL  STRESSES  l\  BEAMS. 
Maximum  Unit  Stresses. 

104.  When  a  body  (as  a  bolt)  is  under  tensile  (or  comp)  stress 

only,  the  tendency  of  the  body,  as  regards  sections  normal  to  the  stress,  is  to 
pull  apart  (or  crush  together)  in  the  direction  of  the  stress,  or  normally  to  the 
section,  and  the  entire  stress  acts  normally  upon  the  section;  but,  on  planes 
oblique  to  the  stress,  the  stress  is  resolved  into  two  components,  one  (n) 
of  tension  (or  comp)  normal  to  the  plane,  and  one  (0  tangential  to  the 
plane  (shearing  stress). 

105.  Under  shearing1  stress  alone,  the  effect,  upon  a  plane  parallel 
to  &  betw  the  2  shearing  forces,  is  pure  shear;    but,  upon  planes  oblique 
to  the  forces,  the  shearing  forces  are  resolved  into  (t)  tangential  or  shearing 
stresses,  and  (n)  normal  (tensile  or  comp)  stresses. 


If' 


Fig.  17. 

1O6.  Thus,  Fig  17,  let  a  bar,  of  length,  L,  and  depth,  D,  be  subjected  to 
a  tension,  S  =  S',  in  line  with  its  hor  axis,  and  to  two  pairs  of  forces,  V=  V' 
and  H  =  H',  as  shown;  V  and  V  constituting  a  right-hand  vert  shear,  while 
H  and  H'  constitute  a  left-hand  hor  shear. 

Suppose  the  bar  divided  by  a  section,  as  N  N,  F  G  or  K  M,  and  consider 
the  forces  acting,  in  either  case,  upon  the  right-hand  segment  of  the  bar  as 
thus  divided. 

Upon  the  normal  section,  N  N,  the  tension,  S,  and  the  hor  shear,  H,  act 
normally  (S  as  tension,  H  as  compression),  and  the  vert  shear,  V,  tangen- 
tially  (as  shear);  but,  for  an  oblique  section,  F  G  or  K  M,  we  first  resolve 
each  force,  S,  V  and  H,  into  two  components,  b  and  y,  c  and  z,  a  and  x, 
respectively  normal  and  parallel  to  the  section,  as  shown  by  the  force-triangles 
on  the  right.*  Then,  summing  these  comps,  algebraically,  we  obtain  the 
resultant  forces,  Pn  (normal)  and  Pt  (tangential  or  shearing),  acting  upon 
the  section  in  question.  With  the  forces,  S,  V  and  H,  as  shown  in  Fig  17, 
we  have: 


On  sec  F  G, 


+   z 


Pt,  right-hand  shear,    =   a  +  c  —  b  ; 


On  sec  K  M,        Pn  ,  compression,    =   a  +  c  —  b  ; 

Pt ,  right-hand  shear,  =   y  +  z  —  x. 

1O7.  If,  now,  we  examine  all  possible  planes  cutting  the  body  at  a 
given  point,  we  shall  find  (1)  one  such  plane  upon  which  the  resultant 
unit  tensile  stress  reaches  its  max;  (2)  another,  normal  to  (1),  upon  which 
the  resultant  unit  comp  stress  reaches  its  max;  and  (3)  two  planes,  normal 
to  each  other  &  bisecting  the  right  angles  betw  planes  (1)  &  (2).  Upon 
the  two  planes  last  named,  (3),  the  resultant  unit  shearing  stresses  reach 
their  max. 

*In  order  that,  for  either  force,  S,  V  or  H,  the  two  force-triangles  (for 
the  two  sections,  F  G  and  K  M)  may  be  identical,  and  thus  simplify  the 
figure,  we  take  the  two  sections,  F  G  and  K  M,  normal  to  each  other. 


4945 


STRENGTH   OF   MATERIALS. 


Fig.   18. 

1O8.  Let  Fig.  18  represent  a  small  element  in  a  bar  under  tensile  & 
shearing  stresses;  and  let  it  be  required  to  determine  the  positions  of 
these  planes  and  the  corresponding-  max  stresses.  Let 

s  =   the  original  normal  (tensile  or  comp)  unit  stress  ; 

v  =     "         "        vertical  (shearing)  unit  stress ; 

=  h  =     "         "         horizontal  (shearing)  unit  stress ; 

s  =     "    max  or  min  resultant  normal  unit  stress  ; 

vr  =     "    max  resultant  shearing  unit  stress  ; 


=     "    angle  betw  s  and  s 


Then 


•CD 


If  8  is! 


'    ]/ (s/2)2  +  v* (2) 

lax  =    s/2   +   VT   =    s/2   4-  ;/ (s/2)2   +  v2 (3) 

iin   =    «/2   —  vr   =    s/2    —  l/  (8/2)2   +   v2 (4) 

'  tension 


sign  gives  max  tension 

'      comp   =   min  tension 
f    +  '     comp 

{    —      "         "          '     tension  =   min  comp. 


1O9.    Example.    Let 

8  =  2000  Ibs/sq  inch,  tension  (not  drawn  to  scale); 

v  =    h     =  1600   "  /  "     "   ,  shear      (  "  '    ). 

Here  v  is  left-handed,  h  right-handed.     If  this  be  reversed,  the  angle,  A, 
betw  the  resulting  tension,  sn  ,  &  the  hor,  will  be  below  the  neut  axis. 


11O.    Then  tan  2  A  =   --    = 


=58°;     A   =   29° 


V  (s/2)2  + 
s/2  + 
s/2  - 


=  v/10002  +  16002  =  1887; 

=    1000  +  1887   =  2887  (tension); 

=    1000  —  1887  =  —  887  (comp). 


111.  In  other  words,  we  have,  as  resultants.  (1)  a  max  unit  tension, 
s  max  =  2887  Ibs/sq  in,  forming  an  angle,  A  =  29°,  with  the  axis  of  the 
bar  or  with  the  direction  of  s  ;  (2)  a  min  unit  tension  or  max  comp,  s  min  = 
—  887  Ibs/sq  in,  normal  to  s  max;  (3)  a  right-hand  unit  shear,  vf  =  1887 
Ibs/sq  in;  and  a  left-hand  unit  shear,  —  v  =  —  1887  Ibs/sq  inch;  the 


DIAGONAL   STRESSES    IN    BEAMS. 


494  C 


directions  of  the  shearing  stresses  bisecting  the  right  angles  betw  the  max 
normal  stresses. 

1 1 2.  The  max  tension   and   compression,  at  any  point,   are  called   the 
**  principal  stresses  "  for  that  point. 

Horizontal  and  Vertical  Shear  in  Beams. 

See  also  pp  440  &c,  446  &c,  450  to  453,  478-9. 

113.  Let  Fig.  19  represent  the  left  half  of  a  homogeneous  beam,  of 

rectangular  section;  breadth,  b,  =  1  inch;  depth,  d,  =  10  ins:  span,  L,  =  100 
ins;  with  cen  load,  W*  of  200  Ibs;  left  reaction,  R  =  W/2  =  100  Ibs.  Weight 
of  beam  neglected.  The  bendg  mom,  at  cen  of  span,  is  M  =  RL/2  = 
PFL/4*  =  5000  inch-lbs;  and  the  mom  decreases  uniformly,*  from  its  max, 
at  cen  of  span,  to  zero  at  the  supports.  In  the  extreme  upper  &  lower  fibers, 
the  longitudinal  unit  stress,  (T  10,  p  468)  s,  =  MT/I,  where  T  =  df2  = 
dist  from  neut  axis  to  extreme  fibers  =  5  ins;  /  =  inertia  mom  of  cross 
section  =  bd*/12  =  1000/12.  Hence,  in  Fig  19,  s  =  12  X  5  M /1000  = 
0.06  M.  Now  s,  being  thus  proportional  to  M,  also  decreases  uniformly,* 
from  its  max,  at  cen  of  span,  to  zero  at  the  supports.  Values  of  M  and  of 
s,  for  the  sections  0,  a,  b,  c,  d,  e,  are  figured  on  the  diagram. 

d 


-_. 

h~~*-::l 



„_.--».-. 

-»% 

i 

'   _==-: 

_-4—  ~-  

=---  K  

T"~" 

\ 

\          8 

i          % 

w 

^=~ 

[ 

n 

\       '/ 

/ 

/ 

/'               «K 

^              o 

/\ 

^^: 

T 

I 

/  '                 '' 

;  i               / 

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~/? 

j 

V- 

*  • 

it* 

:i 

i 
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10"               2 
1000             20 
60               IS 

0"               3 
00             30 
JO               li 
L       w" 

0"              41 
00             40 
50              24 

3"              5 
00             50 
Q               3( 

0" 

S? 

z       w 

Fig.  19. 


*  Under  a  uniformly  distributed  load,  the  bendg  mom,  at  cen  of  span, 
is  WL/8;  and  the  bendg  moms,  M,  and  the  resulting  longitudinal  unit 
stresses,  s,  vary  as  the  ordinates  of  a  parabola,  as  indicated  by  the  dotted 
parabola,  r  me,at  top  of  Fig  19,  which  corresponds  to  a  uniform  load  =  400 
Ibs  =  2  W,  The  unit  shears,  v,  in  a  given  hor  section,  then  decrease  uni- 
formly, from  a  max,  at  the  supports,  to  zero  at  the  cen  of  the  span.  Com- 
pare 3d  and  4th  figures,  p  474. 


494  d 


STRENGTH    OP    MATERIALS. 


114.  The  unit  hor  tensile  and  eoinp  stresses,  s,  at  the  several  points 
in  any  vert  section,  are  proportional  to  the  (lists  of  those  points  from 
the  neutral  axis,  as  indicated  by  the  diagram  at  each  vert  section,  Fig  19. 

115.  In  Fig  20,  let  n  and  g  be  two  vert  sections  of  this  beam,  such  that, 
at  n  and  at  g,  the  extreme  unit  fiber  stresses  are:  m  n  =  15,  and  u  g  =  25, 
respectively.     Then  the  rectangular  portion,  n  f,  of  the  beam, 
betw  sections  n  A  g,  is  acted  upon  by  a  series  of  net  or  resultant  forces, 
ranging  from  compression,  e  g  =  u  g  —  m  n  =  —25  —  (—15)    =  —10,  at 
the  top,  to  tension,  =  +10,  at  bottom,  as  indicated  by  the  diagram,  e  k. 

116.  Suppcfse  the  piece  nf  to  be  divided  into  10  hor  strips  of  equal  depth, 
=  1  inch.     Then  the  net  unit  stresses,  s,  acting  at  the  tops  and  bottoms 
of  these  strips,  respectively,  are  those,  (—10,  —8,  —6,  ...  .6,  8,  10)  figured 
from  e  to  k;    and  the  mean  stress,  or  (since  depth  of  each  strip  =  6  =  1) 
the  force,  acting  upon  each  strip,  is  that  (—9,  —7,  —5,  ...  .5,  7, 9) 
figured  betw  g  and  f. 

117.  These  forces  are  transmitted,  from  strip  to  strip,  thru  their 
surfs  of  contact;    and,  in  determining  the  shearing  force,  acting  in  the  hor 
plane  betw  any  2  strips,  we  regard  the  upper  (or  lower)  strip  as  acted  upon 
by  its  own  push  or  pull  plus  (algebraically)  those  of  all  the  strips  above  (or 
below)  it. 


25- 


118.  Thus,  the  3d  strip  from  the  top  is  pushed  to  the  left  by  a  force  of 
—  9  —  7  —  5  =  —  21,  while  the  4th  strip,  just  below  it,  is  pulled  to  the  right 
by  a  force  of  9  +  7  +  5  +  3+1—  1—3    =   21.     Hence    the    surf  betw 
the  3d   and  4th  strips,  sustains  a  counterclockwise  shear  of  21  ;    which, 
divided  by  the  area,  6  I  =  I,  of  that  surface,  gives  the  unit  shear  in  the 
plane  betw  the  3d  and  4th  strips.     With  central  load,*  this  unit  shear  is 
uniform  from  each  support  to  cen  of  span,  where  it  changes  sense  (from  plus 
to  minus,  or  vice  versa)  but  is  of  the  same  intensity  in  the  other  half-span. 
See  3d  Fig,  p  474. 

119.  In  any  vert  section  of  the  beam,  let 
V     =  the  total  shear 

=     "    reaction  of  either  support,  minus  the  sum  of  all  loads  betw 

that  support  and  the  section  ; 

/      =    "    inertia  moment  with  respect  to  the  neut  axis; 
b      =    "    breadth;  d  =  depth  ; 

a      =    "    area  above  (or  below)  any  given  point  in  the  section; 
c      =    "    dist  from  neut  axis  to  grav  cen  of  a; 
Ms  =  a  c  =  static  mom  of  a,  with  respect  to  the  neut  axis; 
v      =  the  unit  vert  shear  =  unit  hor  shear  at  a  given  point. 

120.  Then 


*  See  foot-note  p  494  c. 


DIAGONAL    STRESSES    IN    BEAMS.  494  6 


At  the  neut  axis,  Mg  (=   a  c) 
Hence,  at  the  neutral  avis: 

v  =  v  *  =  F  -1-2. 

* 


2      bd 


=  ---    X   the  mean  vert  shear  in  the  cross  section. 
See  also  Uf  51  etc. 

Since,  under  a  center  load,  (1[  113  and  Fig  19)  s  increases  uniformly,  from 
zero  (at  support)  to  smax  (at  span  center),  we  have,  for  the  increase  of  «,  in 
any  portion,  as  n  g  =  I,  Fig  20,  of  the  span  : 

sg  —  sn  =   Smax   /-"TO    =   ^  smax  j-  . 


131.  At  the  left  of  Fig.  19  is  a  diagram  showing  the  unit  shears 

in  the  several  hor  sections. 

122.  Let  Fig  21  represent  a  small  element  of  a  body,  of  unit  thickness, 
normal  to  the  paper,  and  acted  upon  by  a  right-hand  vert  shear,  V  =  v  D, 
(where  v  =  the  unit  vert  shear,  and  D  =  the  depth  of  the  element)  and  by  a 
left-hand  hor  shear,  H  =  h  L  (where  h  =  the  unit  hor  shear,  and  L  =  the 
length  of  the  element).  For  equilib  of  moments,  we  must  have 

V  L  =  H  D\       orvDL  =  hLD;       or  v  =  h. 
In  other  words, 

unit  vert  shear  =  unit  hor  shear. 


I 


Fig.   21. 

Ufaximum  Unit  Stresses  in  Beams. 

123.  The  common  theory  of  beams  (pp  466  to  494,  t  f  1-103) 
considers  only  the  longitudinal  tensile  and  compressive  forces 

and  the  vert  and  hor  shearing  forces,  due  directly  to  the  load  and  to 
the  upward  reactions  of  the  supports,  and  acting,  at  any  point,  upon  vert 
and  hor  planes  passing  thru  such  point;  but,  except  in  certain  limited  por- 
tions of  the  beam,  these  stresses  are  not  the  maximum  stresses  act- 
ing at  such  point;  for  they  combine  to  form  resultant  diagonal  stresses, 
acting  upon  diagonal  planes  (passing  thru  the  same  point);  and,  upon  some 
of  these  diag  planes,  the  resulting  normal  and  tangential  stresses  are  greater 
than  either  of  the  original  stresses. 

124.  The  common  theory  is  sufficiently  well  adapted  to  beams  of 
many  kinds,  and  especially  to  steel  beams,  where  the  longitudinal  forces 
are  resisted  by  the  flanges,  and  the  shears  by  the  web;  but  in  certain  por- 
tions of  deep  and  heavily  loaded  beams,  especially  those  of  reinforced 
concrete,    the   diagonal    resultant    or   maximum  stresses  are    the 
riding  stresses,  and  must  not  be  neglected. 

125.  In  a  beam,  at  top  and  bottom,  we  have,  respectively,  hor  tensile 
and  comp  stresses  only,  and,   at  the  neut  axis,  shear  (vert  &  hor1)  only; 
but,  at  all  other  points,  we  have  shear  (vert  &  hor)  acting  conjointly 
with  hor  stresses,  either  tensile  or  comp.  At  all  points.these  shearing  and 
longitudinal  stresses  may  be  resolved   into  components,  normal  & 
tangl  to  any  plane,  at  pleasure,  as  in  the  case  of  the  bar  or  bolt,  Fig  17. 


494/ 


STRENGTH   OF    MATERIALS. 


126.  Thus,  each  element  of  the  beam,  Figs  22,  23,  24,  is  acted  upon  by 
hor  &  vert  forces  (unit  stresses),  which,  acting  upon  diagonal  planes,  are 
resolved  into  diagonal  components,  and  these  components  may  be  alge- 


1 

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rig.  22. 


Section 


Fiff.  24. 


braically  summed  into  resultants:  but  the  original  stresses  vary  in 
intensity,  and  the  resultant  stresses  both  in  intensity  and  in  direction,  from 
point  to  point.  For  the  directions  and  values  of  these  resultant 
stresses  at  their  maxima,  we  have,  from  Eqs  1-4,  fllOS,  p  4943: 

Tan  2  A   = 


-(2) 


where 


8/2  ±  vr    =    s/2  db   l/(«/2)» 


s     =   original  unit  tensile  or  comp  stress  at  the  point ; 

v    =   original  (vert  or  hor)  unit  shear  at  the  point. 
The  max  normal  stresses,  s~,  are  called  the  principal  stresses. 
127.  Applying  these  formulas  at  numerous  points  in  the  profile  of  the 
beam,  Fig  22,  we  are  enabled  to  construct  curves.  Fig  23,  showing  the 
directions  of  the  stresses  ;  and  to  plot,  as  in  Fig  24,  for  given  points,  the 
directions  and  intensities  of  the  stresses  there  acting.     At  any  given 
point,  Fig  24,  we  have  resultant  normal  and  shearing  stresses  analogous  to 
those  in  Fig  18,  p  494  6;  but,  in  the  present  Fig  24,  owing  to  want  of  space, 
only  the  max  principal  stress,  s_  max,  is  shown  for  each  point  selected. 


DIAGONAL    STRESSES   IN    BEAMS.  494  £ 

128.  In  Fig.  23,  the  directions  of  the  principal  stresses,  sp  ,  are  repre- 
sented by  the  solid  curves;  those  of  thie  resultant  shears,  VT  ,  by  dotted 
curves. 


Of  the  solid  curves 
(principal  stresses) 

concave 

horizontal 
at  cen  of  span 

at  45° 
with 

at  90° 
with 

The  tension  curves  are 
The  compression  curves  are 

upward 
downwd 

below  neut  axis 
above     ' 

neut  axis 

top  of  beam 
bot  " 

The  tensile  and  comp  curves  are  normal  to  each  other  at  their  intersections. 

129.  Following  any  curve  (concave  upward)  of  normal  tension,* 
we  find  that, 

(1)  for  its  point  of  tangreiicy  with  the  hor  (viz:   at  cen  of  span) 
»    max  =  tension  =  s  ;       s_  min  =  comp  =  0  ; 

(2)  for  the  point  where  the  curve  crosses  the  neut  axis  (at  45°) 
»„  max  (tension)  =  «„  min  (comp)  =  vr  —  ±v  (shear); 

(3)  above  the  neut  axis,  the  tension  becomes  sp  min,  and  continues 
diminishing,  as  the  direction  approaches  the  vert,  becoming  zero  at  top, 
where  A  =  90°.     Above  the  neut  axis,  for  points  in  the  same  curve,  the 
compression  (normal  to  the  curve)  is  now  s    max,  and  increases  from  s_  = 
vr  =  ±v,  at  the  neut  axis,  to  s    max  (comp)  =  s,  at  top. 

130.  Where  v  =  zero  (viz:    at  any  point  in  the  vert  cross  section  at 
cen  of  span,  and  along  the  extreme  upper  and  lower  fibers),  we  have  (1{  126)  : 

vf  =  s/2 

sp  max  =  s/2   +    vf  =   s ;         tan  2  A   =  0 ; 

sp  min    =   s/2  —  vf  =   0  ;         tan  2  A   =  0. 

131.  The  equation,  tan  2  A  =  0,    gives  either  2  A  =  0°  or  2  A  =  180°; 
i.  e.,  A  —  0°,  or  A  =  90°;    but  we  know  that,  at  cen  of  span  and  along  the 
extreme  upper  and  lower  fibers,  sp  max  is  hor,  or  A  =  0°;  and  «„  min  is  vert, 
or  A  =  90°. 

132.  Where  s   =   zero  (as  at  the  neut  surf  and  where  bending  mom 
=  zero),  we  have  (t  126)  :  vr  =  ±v  ;      s    max  =  sp  min  =    \/v2  =   +v; 
tan  2  A   =    oo  ;        2  A   =  90° ;       and  A   =   45°. 

133.  Of  the  (dotted)  shear  curves,  Fig  23,  those  of  one  set  are  tan- 
gential to  the  neut  axis  and  reach  top  &  bottom  of  beam  at  angles  of  45°, 
tending  away  from  cen  of  span;    while  those  of  the  other  set  are  normal  to 
these  and  to  the  neut  axis  at  their  intersections,  reaching  top  and  bottom 
of  beam  at  45°,  tending  toward  cen  of  span. 


MOMENTS  IN   CONTINUOUS  BEAMS. 

See  also  1ffl  78,  etc. 

134.  Figs  25  and  26  show  positive  and  negative  bending  moments 
in  two  continuous  beams,  Fig  25  of  two  equal  spans,  and  Fig  26 
of  three  equal  spans,  resting  freely  upon  their  supports.  Each  span  =  1. 
Fig  26  (three  spans)  may  be  used,  with  sufficient  approximation,  for  cases 
where  the  spans  are  more  numerous. 

*  Conversely  for  curves  (concave  downward)  of  normal  compression. 


494  A 


STRENGTH    OF   MATERIALS. 


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135.  At  any  cross  section,  the  ordinate,  betw  the  axis,  0  X,  of  abscissas, 
and  the  curve,  (1)  mw,  (2)  mp  pos,  or  (3)  m    neg,  represents,  respectively, 
by  the  scale  of  ordinates  on  the  left,  (1)  the  dead  load  moment,  mw,  (2)  the 
max  positive  live-load  mom,  mp  pos,  or  (3)  the  max  negative  live-load  mom, 
mp  neg,  at  that  section,  the  dead  load  (1  per  unit  of  span)  being  uniformly 
distributed  over  the  entire  length  (two  or  three  spans,  as  shown)  of  the  beam, 
and  the  live  load  (1  per  unit  of  span)  being  uniformly  distributed  alternately 
over  two  portions  of  the  length  of  the  beam,  said  portions  being,  for  each 
cross  section,  such  that  the  uniformly  distributed  live  load,  placed  upon  said 
portions,  will  produce,  alternately,  the  max  pos  and  the  max  neg  mom  at 
that  section. 

136.  In  an  actual  beam,  at  any  point,  we  have,  for  bending  mom: 

M  =  mw  w  U  +  mp  p  V  ; 
where 

mw  =  the  ordinate,  at  the  point,  from  0  .Y  to  the  curve  mw ; 

mp  =    ".     ' '       "    "    "        " 

w     =  uniform  dead  load  per  unit  of  span; 

p     =  live  "    ,  placed  as  explained  in  If  135. 

L     =  the  actual  span. 

Thus,  at  the  point,  a,  Fig  26  (distant  0.7  L  from  0),  we  have,  by  scale, 
mw   =   0.035;  mp  pos  =  0.070;       mp  neg  =  —  0.035.     Hence,  at  point  a, 

max  pos  mom  =  0.035  w  L2  +  0.070  p  L2; 
max  neg  mom  =  0.035  w  L2  —  0-035  p  L2. 

If,  therefore,  p  =  w,  the  max  neg  mom,  at  a,  is  zero,  and  there  is  no 
resultant  neg  mom  to  the  left  of  a;  but,  if  p    =    2  w,  we  have  w  =  p/2  = 
(w  +  p)/3;   and,  at  a,  with  p  =  2  w  : 
max  neg  mom  =  0.035  w  L2  —  0.035  X  2  w  L2 

=  0.035  w  L2  —  0.070  w  L2  =  —  0.035  w  L2 

=  —  0.035  (w  +  p)  L2/3. 


930  CEMENT   MORTAR. 

MORTAR. 

Cement. 

For  experiments,  see  p  1135. 
For  specifications,  see  pp  937,  940,  942,  1184. 

For  Concrete,  see  pages  1084,  etc. 
For  abbreviations,  symbols  and  references,  see  p  947 1. 

1.  The  property  of  setting  and  hardening  under  water  is  called  hydrau- 
licity;  and  cements,  which  harden  under  water,  are  called   hydraulic 
cements:  or,    more    briefly,    cements.     For    behavior   of   cement 
when  mixed  with  water,  with  or  without  sand,  see  Mortar,  p  947  d. 

Materials. 

2.  The  elements,  chiefly  concerned  in  the  action  of  lime  and 
cem  mortars,  are — 

Calcium,  Ca  ] 

Aluminum,  Al 

Carbon,  C    \     Oxygen,  O. 

Silicon,  Si 

Hydrogen,  H   J 

3.  Oxygen    combines  with  each  of  the  others,  forming  oxides. 
Thus  :  Calcium  oxide,  CaO,  is  lime; 

Aluminum  sesqui-oxide,  Al2Os,*  is  alumina; 
Carbon  dioxide,  CC>2,  is  carbonic  acid ; 
Silicon  dioxide,  SiO2,  is  silica,  or  silicic  acidjf 
Hydrogen  monoxide,  H2O,  is  water. 

4.  The  materials  most  used  in  the  manufacture  of  cements  are  either 
(a)  calcareous,  (b)  argillaceous,  or  (c)  both  calcareous  and  argillaceous. 

(a)  Calcareous  (rich  in  lime  carbonates). 

Limestone,  a  lime  carbonate,  or  combination  of  lime  and  carbonic  acid, 
CaO  +  CO2,  or  CaCO3.  Marble  is  limestone. 

Dolomite,  or  magiiesian  limestone,  containing  about  45  per  cent 
of  magnesia  carbonate,  MgO.  CO2.  Where  strata  of  limestone  and  dolomite 
adjoin,  the  rock  varies  in  composition  between  the  two,  containing  percent- 
ages of  magnesia  carbonate  varying  from  0  to  45. 

Chalk,  a  soft  limestone,  composed  of  remains  of  marine  shells. 

Marl,  a  soft  and  impure  hydrated  J  lime  carbonate,  precipitated  from 
still  water  and  found  in  the  beds  and  banks  of  extinct  or  existing  lakes. 

Alkali  waste,  lime  carbonate,  precipitated,  as  a  waste  product,  in  the 
manufacture  of  caustic  soda. 

Coral.     See  H  5. 

(b)  Argillaceous  (rich  in  alumina  silicates). 

Clay  (including  argillaceous  minerals  in  general),  an  alumina  silicate,  or 
combination  of  alumina  and  silicic  acid,  A12O.3  +  SiO2. 

Shale  and  slate,  clay,  solidified  by  geological  processes. 

Puzzolana,  or  pozzuolana,  a  volcanic  slag,  found  at  Puzzuoli,  or  Poz- 
zuoli,  near  Mount  Vesuvius,  an  impure  alumina  silicate. 

Blast  furnace  slag,  practically  an  artificial  puzzolana. 

Brick-dust.  See  «  r>. 

(c)  Rich  in  both  lime  carbonate  and  alumina  silicate. 
Cement  rock  is  argillaceous  (clayey)  limestone.     The  alumina  silicate 

usually  ranges  from  13  to  35  %.     There  is  generally  a  considerable   per- 
centage of  magnesia  carbonate,  amounting  sometimes  to  25  %. 

5.  A  soft  coral  rock,  from  the  reefs  near  Colon,  Panama,  mixt 
with  clay  and  silt  brought  down  by  the  Chagres  river,  or  with  "a  pumiceous 
rhyolite  tuff,"  found  on  the  Isthmus,  or  with  both,  and  crushed,  burned  and 
tested  at  the  Lehigh  Valley  Testing  Laboratory,  at  Allentown,  Pa.,  gave  a 

*The  subscripts  indicate  the  combining  ratios  of  the  several  elements. 
Thus,  in  alumina,  A12O3  means  a  compound  of  2  atoms  of  alumina  with  3 
of  oxygen. 

t  Quartz  is  silica;  and  most  of  the  sand,  used  in  mortar,  is  quartz  sand. 

%  Hydrated;  containing  chemically  combined  water. 


CEMENT.  931 

uniform  cement,  comparing  favorably  with  average  standard  brands  of 
Lehigh  cement.  The  coral  rock  is  "a  remarkably  pure  lime  carbonate." 
The  Chagres  clay  and  silt  are  "rather  low  in  silica,  but  contain  a  relatively 
large  amount  of  iron  as  compared  with  alumina."  The  tuff  "is  of  approx- 
imately the  same  composition  as  the  argillaceous  materials  used  in  the 
Lehigh  district  of  Pennsylvania. "  (Ernest  Howe,  U.  S.  G  S,  E  N,  '07/Nov/ 
21,  p  544.)  See  HH  29,  etc. 

6.  Mr.  Ernest  McCullough  "mixed  fine  brick  dust  and  hydrated 
lime  together    and  made  a  fairly  satisfactory  cem  for  a  small  concrete 
job  in  a  locality  where  Portland  cem  could  not  be  obtained."     (E  N,  '07 / 
Nov/21,  p  557.) 

7.  Iiime.     When   limestone    (without   clay)   is   "burned,"   its   CC>2  is 
driven  off,  and  the  remaining  ("quick")  lime  has  a  strong  affinity  for 
water,  absorbing  it  with  such  avidity  as  to  develop  heat  sufficient  to  pro- 
duce steam,   the   generation  of  which  disintegrates  and  swells  the  mass. 
Combining  thus  with  the  water,  the  lime  forms  calcium  hydrate,  CaO.H2O,  or 
CaH2O2.     This  process  is  called  slaking  or  slacking? ;  and  lime  which 
has  satisfied  its  affinity  for  water  is  called  slaked  (or  slack)  lime.     When 
slaked  lime  is  used  as  mortar,  it  gradually  absorbs  carbonic  acid  from  the 
air,  forming  lime   carbonate,    the   water   being   liberated   and   evaporated. 
Hardened  lime  mortar  may  thus  be  regarded  as  an  artificial  limestone. 

Manufacture. 

8.  Cement.    When  alumina  silicate,  such  as  clay,  in  sufficient  quantities, 

is  "  burned  "  with  calcium  carbonate,  such  as  limestone,  the  burned  prod- 
uct, called  cement,  is  deficient  in,  or  devoid  of,  the  slacking  property;  but, 
on  the  other  hand,  when  it  is  made  into  mortar,  the  combinations,  formed 
between  the  elements  of  the  lime,  the  alumina,  the  silica  and  the  water, 
during  the  burning,  and  afterward  in  the  mortar,  are  such  that  they  readily 
proceed  under  water.  Chemists  differ  as  to  the  nature  of  these  combina- 
tions, except  that  these  constitute  a  process  of  crystallization,  resulting 
chiefly  in  the  formation  of  hydrated  lime  silicate  and  hydrated  lime  alumi- 
nate,  which  two  compounds  constitute  the  major  portion  of  most  cems. 

Natural  and  Portland  Cement. 

9.  In  the  manufacture  of  "  natural "  cement,  cement  rock,  broken 
into  lumps,  is  first  calcined,  at  from  1000°  to  1400°  C  (1800°  to  2500°  F)  in 
a  stationary  kiln,  in  alternate  layers  with  coal  of  about  pea  size,  as  fuel. 
It  is  then  ground  to  a  fine  powder,  and  this  is  sometimes  specially  mixed, 
in  order  to  increase  its  uniformity. 

10.  The  qualities  of  nat  cems  vary  widely,   owing   to  diffs   in   the 
compositions  of  cem  rocks  found  in  diff  localities. 

11.  The   name   Rosendale,  originally  and  properly  restricted    to   nat 
cems  made  in  Ulster  County,  N  Y,  was  at  one  time  applied  indiscriminately 
to  American  nat  cems  in  general. 

12.  In  Europe,  quick-setting  nat  cems  are  called  "  Roman  cements." 

13.  Portland  cement  was  so  called  on  account  of  the  resemblance  of 
the  hardened  mortar  to  Portland  stone,  the  oolitic  limestone  of  Portland, 
England. 

14.  Portland   cem   is  made   from   different   combinations  of  the   cal- 
careous and  argillaceous  materials  named  in  K  4,  and  these  require  different 
preliminary  treatments.     Thus,  hard  rock  is  crushed;  soft  rock  and  clay  are 
ground;  marl  and  clay  are  mixed  wet,  and  the  marl  is  sometimes  pumped 
to  the  mill.     In  any  case,  the  resulting  materials  are  dried  and  finely  ground, 
mixed,  and  then  calcined  at  a  temperature  of  1450°  to  1550°  C,  or  say  2600° 
to  2800°  F,  producing  incipient  vitrifaction,  which  consists  of  the  chemical 
combination  of  the  silica,  alumina  and  lime,  into  a  glassy  clinker,  essentially 
a  lirne  silicate  and  aluminate.     The  resulting  clinker  is  again  ground  to  an 
impalpable  powder,  which  is  the  finished  product. 

15.  The  proportions  of  the  several  materials  are  carefully  adjusted. 
There  is  usually  from   74  to  77.5  %  lime   carbonate,  and   about  20  %   of 
alumina  silicate  and  iron  oxide.     See  H  32. 

16.  Manipulation.  The  raw  material  is  sometimes  molded  into  bricks 
which  are  burned  in  a  stationary  kiln;  but  it  is  now  more  generally  fed,  as 
a  fine  powder,  into  the  upper  end  of  a  nearly  hor  cyl  (rotary  kiln)  6  to  8  ft 


932  CEMENT   MORTAR. 

in  diam  and  from  60  to  100  ft  or  more  in  length.  Coal  dust,  as  fuel,  is  in- 
jected, by  an  air  blast,  into  the  other  end;  while  most  of  the  air,  required 
for  combustion,  is  admitted  freely  from  the  atmosphere  thru  other  openings. 

17.  As  in  the  case  of  lime,  the  burning-  drives  off  the  carbonic  acid 
and  water,  and  more  completely  oxidizes  any  iron  present. 

18.  The  higher  cost  of  Portland  cement  is  due  to  the    more 
careful  selection  of  the  materials  and  to  the  more  elaborate  and  expensive 
treatment  given  them,  resulting  in  the  ultimate  attainment  of  much  greater 
strength  and  uniformity  than  are  usually  found  in  nat  cems. 

19.  The  improvements,  which  have  been  made  in  the  manufacture 
of    Portland   cement,  are   driving   out   other   makes.     Owing   to   its 
greater  sand-carrying  capacity,  it  is  often  used,  by  contractors,  even  where 
the  specifications  permit  the  use  of  nat  cem. 

20.  Overburningr  is  liable  to  occur,  if  the  material  is  deficient  in  lime 
("over-clayed").     Underburning  yields  a  soft  brownish  clinker,  and 
weak,  quick-setting  cem,  heating  in  water.     Some  cems,  slow  at  first,  be- 
come quicker  after  storage. 

21.  Portland  Cement  is  used  for  structures  subjected  to  severe  or 
repeated  stresses,  for  cases  where  high  strgth  must  be  attained  in  a  short 
time,  for  concrete  buildings,  where  water  will  be  in  contact  with  new  work, 
for  thin  walls  subject  to  water  pres,  and  for  work  exposed  to  abrasion  or  to 
weather;  while  natural  cement  may  be  used  in  dry  sheltered  founda- 
tions under  compressive  loads  not  exceeding  75  Ibs  per  sq  inch  and  not 
imposed  until  3  months  after  placing,  for  backing  and  filling  in  massive 
cone  or  stone  masonry  where  wt  and  mass  are  desiderata,  and  for  street  and 
sewer  foundations. 

Pnzzolana. 

22.  Slag  cements  (sometimes   called   puzzolana   cements  or  puz- 
xolana)  are  intimate  mixtures  of  slaked  lime  and  basic  blast-furnace  slag, 
both  finely  ground,  and  not  calcined.     As  the  slag  leaves  the  blast-furnace, 
it  is  chilled  and  disintegrated  by  running  it  into  water.     A  little  soda  is 
sometimes  added,  to  hasten  setting.     Slag  cem  is  not  to  be  confounded  with 
those  Portland  cems  in  which  slag  is  one  of  the  ingredients. 

23.  In  dry  air,  the  sulphides,  contained  in  Puzzolana  cement,  oxi- 
dize, and  cause  superficial  cracking.     It  sets  more  slowly  than  Portland, 
unless   treated   with   soda.     If  so   treated,    the  soda  becomes   carbonated 
under  long  storage,  and  the  cem  again  becomes  slow-setting.     Since  puzzo- 
lana cem,  properly  made,  contains  no  free  or  anhydrous  lime,  it  does  not  warp 
or  swell,  and  requires  less  water  than  Portland;  but,  for  permanency  after 
placing,  the  finished  work  should  be  kept  constantly  moist.     It  is  recom- 
mended for  use  in  sea  water,  alone  or  mixed  with   Portland.     Its  mortar 
ia   tougher  than   Portland,  but  never  becomes  so  hard.     It  should  not  be 
subjected   to   attrition   or   blows.     (Report,  Board  of    U  S  Engr  officers, 
U.  S.,  Prof'l  Papers  No  28,  '01.) 

24.  Puzzolana  cement  is  said  to  work  well  if  used  with  2  or  3  parts 
sand  and  not  subjected  to  freezing  weather.     Its  ingredients  must  be  finely 
ground   and  intimately  mixed.     It   is  used   where  extreme  strength   and 
hardness  are  not  required. 

Silica  Cement. 

25.  Silica    Cement,  or    sand    cement,  was  originally  made  by 
mixing  Portland  cem  with  quartz  sand  (silica)  and  grinding  the  mixture  to 
extreme  fineness      It  was  claimed  that  the  cem  thus  became  much  more 
finely  ground,  and  that  "silica  cement,"  containing  one  part  Portland  cem 
and  three  parts  silica,  could  therefore  carry,  in  mortar,  nearly  as  much  sand 
as  could  the  pure  cem  alone;  also  that  mortars,  made  with  silica  cem,  were 
less  permeable  to  water  than  those  made  with  pure  cem  in  the  ordinary  way. 

26.  Owing  to  the  high  cost  of  grinding  the  quartz  sand,  less  refractory 
materials,  such  as  lime-stone,  are  now  substituted  for  it.     The  product, 
so  obtained,  is  still    called  "silica  cement,"  altho  containing  a  less  propor- 
tion of'silica  than  Portland  cem. 

27.  Silica  cement  mortar  is  said  to  work  more  smoothly  under 
the  trowel  than  that  made  with  ordinary  cems. 

28.  In  the  construction  of  a  concrete  lock  at  St.  Paul,  Minn.,  it  was  in- 
tended to  use  1.5  volumes  silica  cem  as  equivalent  to  1  vol  Saylor's  Port- 


CEMENT. 


933 


land;  but  experiments  indicated  that,  at  6  mos,  concrete,  made  with  silica 
cem,  was  as  strong  as  that  made  with  Portland. 

Other  Cements. 

29.  White  Portland  cement,  obtained  by  making  certain  modifi- 
cations in  the  process  of  manufacture,  is  nearly  colorless.  It  is  suitable  for 
making  imitation  marbles,  etc.,  and  capable  of  taking  artificial  coloring. 
It  is  higher  in  price  than  ordinary  Portlands.  See  If  44. 

SO.  Iron  ore  cement  ("Erz-cement"),  Krupp  Steel  Co.  In  this 
cem,  the  argillaceous  material  of  Portland  cem  is  mostly  replaced  by  iron 
oxide.  The  material  is  burned  and  ground  as  for  Portland  cem,  HU  13,  &c. 
Spec  grav,  3.31.  Slower  setting  than  Portland.  Sound.  Low  early 
strgths;  but,  in  time,  strgth  far  exceeds  that  of  Portland.  No  trace  of 
expansion  or  crackg  in  sea  water  under  15  atmospheres.  (Wm.  Michaelis, 
Jr.,  Western  Soc  Engrs,  Aug  1907;  S.  B.  Newberry,  Cement  Age,  Jan  1907.) 

31.  Hydraulic  lime  is  a  name  given  to  cems  (much  used  in  Europe) 
which,  while  to  some  extent  hydraulic,  do  not  contain  enough  of  the  hydrau- 
lic elements  to  prevent  slaking.     The  slaking,  however,  is  slower,  and  the 
swelling  less,  than  with  lime  proper. 

Composition. 

32.  Analyses  of  cements,  in  percentages. 
In  each  group  of  three  lines, 

the  upper  line  shows  the  max  percentage. 
"    middle    "  "   mean 

"   lower      "      "         "    min  " 


Silica.  Alumina.  Iron  Oxide. 

SiOz 


Xiwe. 

Ca  O 
•  0  10  20  30  0  10  0  10  20  0  10  20  30  40  50 


Magnesia. 

MgO 
0    10    20 


Fig  1.     Analyses  of  Cements. 

33.  The  ratio  of  the  wt  of  alumina  silicate  to  that  of  the  lime,  in  a  cem, 
is  called  its  hydraulic  index.     Other  things  being  equal,  it  may  be  used 
as  an  indication  of  the  hydraulicity  of  the  cem. 

34.  Thus,  if  a  cem  contains  30  %  alumina  silicate  and  60  %  lime,  its  hy- 
draulic index  is  30/60  =  0.50. 

35.  The  hydraulic  modulus  is  approximately  the  reciprocal  of  the 
hydraulic  index;  i.e.,  the  modulus  is   the  ratio,  by  wt,  of  lime,  to  silica, 

*  Richard  K.  Meade,  "  Portland  Cement,"  1906,  pp  16-17. 

t  E.  C.  Eckel,  "Cements,  Limes  and  Plasters,"  1907,  pp  253  etc.,  667-8. 

1 16  analyses  of  "Steel"  (slag)  cement,  made  by  Illinois  Steel  Co.,  Soufch 
Chicago,  reported  by  Board  of  U.  S.  Engr  Officers,  1900,  gave  practically  the 
same  avs,  but  with  generally  greater  uniformity:  silica,  29.9  to  27.8;  alumina 
and  iron,  12.1  to  11.1;  lime,  52.1  to  50.3;  magnesia,  3.0  to  1.6. 

C3 


934  CEMENT   MORTAR. 

alumina  and  iron  oxide.  It  is  sometimes  specified  that  the  modulus,  in 
Portland  cement,  shall  be  1.7. 

36.  In  natural  cements,  the  modulus  usually  ranges  from  0.667  to  1.667. 

37.  Mr.  Spencer  B.  Newberry  uses  the  ratio  : 

(lime  —  alumina)  -r-  silica, 

which  he  terms  the  lime  factor,  and  which  usually  varies,  iu  the  raw 
material,  betw  2.7  and  2.8,  and,  in  the  best  commercial  cems,  betw  2.5 
and  2.6. 

38.  Mr.  Edwin  C.  Eckel  (Cements,  Limes  and  Plasters,  p  170)  suggests 
the 

Cementation  index  -  2'8*  +   l'1*  +  °'7i 

I   +    1.4m 

where  s,  a,  i,  I  and  m  are  the  percentages,  by  wt,  of  silica,  alumina,  iron 
oxide,  lime  and  magnesia,  respectively. 

39.  The  most  common  adulterants  of  cem  are  ground  limestone,  lime, 
shale,  slag  and  ashes;  and  Portland  cem  is  sometimes  adulterated  with  nat 
cem.     Most  of  the  adulterants  commonly  used  are  merely  inert,  and  there- 
fore only  weaken  the  cem;  but  quick  lime  may  do  more  serious  mischief. 

See  Cement  Mortar,  Iffl  28,  etc.,  p  947  /. 

Properties. 
Fineness. 

40.  Fineness.     Even  in  cem  of  standard  fineness,  the  inner  portions 
of  the  grains  seem  to  remain  inert.     The  finer  the  cem,  the  more  sand  it 
will  carry  and  still  produce  a  mortar  of  a  given  strength;  but,  in  each  case, 
there  is  a  point  where  the  cost  of  additional  fineness  offsets  the  additional 
advantage  which  may  be  gained. 

41.  Hence   fineness  is  less  important  with  natural  than  with  Port- 
land cem;  for  the  cheapness  of  nat    cem    may  render  it  advisable  to  use 
the  cem  in  larger  quantities,  rather  than  pay  for  finer  grinding,  in  order  to 
secure  the  desired  strgth. 

42.  Cements,  ground  to  extreme  fineness,  in  order  to  secure  strgths 
beyond  those  of  commercial  products,  set  so  quickly  that  they  must  be  used 
immediately   after  adding  water.      (VVm.   Michaelis,   Jr.,   Western   Soc   of 
Engrs,  Aug  '07.) 

43.  The  fineness  of  cement  and   sand   is   indicated   as  fol- 
lows,  where  the  large   numerals   represent   the  sieve   numbers;  the   small 
numeral,  to  the  left  of  each  sieve  number,  represents  the  percentage  retained 
upon  that  sieve;  and  the  final  small  numeral,  to  the  right  of  the  last  sieve 
number,  represents  the  percentage  passed  by  the  last  sieve.     The  sum  of  the 
small  numerals   =    100.     Thus,    520    1530    354045   means  that  5  %  were  re- 
tained on  a  No.  20  sieve,  15  %  on  a  No.  30,  and  35  %  on  a  No.  40,  while  the 
remaining  45  %  passed  the  No.  40  sieve. 

Color. 

44.  Color.     The  lime  silicates   and   aluminates,  which   constitute   the 
cem  proper,   are  colorless  when  pure.     (See  White  Cement,   If  29.)     The 
color  of  cems  is  therefore  due  to  other  matter  which  is  unavoidably  present, 
notably  to  the  iron  oxides,  and  may  be  affected  by  either  beneficial,  harmful 
or  neutral  ingredients.     Hence,  color,  in  itself,  is  of  but  little  value  as  a 
guide  to  quality,  but  variations  in  shade,  in  a  given  kind  of  cem, 
may  indicate  diffs  in  the  character  of  the  rock  or  in  the  degree  of  burning. 
Thus,  with  nat  cems,  a  light  color  generally  indicates  an  inferior  or  under- 
burned  rock.     A  coarse-ground  cem,  light  in  color  and  wt,  would  be  viewed 
with  suspicion. 

45.  "With  Portland  cem,  gray  or  greenish-gray  is  generally  considered 
best;  bluish  gray  indicates  a  probable  excess  of  lime,  and  brown  an  excess 
of  clay.     Natural  cems  are  usually  brown,  but  vary  from  very  light  to  very 
dark.     Slag  cem  has  a  mauve  tint — a  delicate  lilac."     (Prof  Ira  O.  Baker, 
"A  Treatise  on  Masonry  Construction,"  p  55.) 

Weight. 

46.  Specific   (gravity  and  weight.     See  spec  grav,  pp.  940,  942. 
The  sp  gr  of  the  solid  particles  of  cem  is  not  affected  by  fineness  of  grinding, 


CEMENT.  935 

but  is  diminished  by  absorption  of  water  and  carbonic  acid  under  exposure, 
and  is  therefore  increased  by  drying.  The  sp  gr  of  Portland  cems  may 
range  from  2.9  to  3.25,  ordinarily  from  3  to  3.2;  nat  cems,  2.7  to  3.2;  Puz- 
zolano  cem,  from  2.7  to  2.9. 

47.  The  weight,  per  cu  ft,  of  cem  powder,  is  affected  by  exposure  and 
by  drying,  as  explained  above,  and  is  increased  by  compression,  as  in  pack- 
ing.    It  is  reduced  by  fine  grinding,  the  finer  particles  packing  less  closely. 
Faija  found  a  loss,  in  wt,  of  about  6  %  in  a  few  days  after  grinding;   17  % 
in  6  mos,  and  21  %  in  a  year. 

48.  In  a  German  Portland  cem,  Eliot  C.  Clarke  found  90  Ibs  per  cu  ft 
when  40  %  was  retained  on  No.  120  sieve,  and  75  Ibs  per  cu  ft  when  so  finely 
ground  that  all  passed  the  same  sieve. 

49.  As  a  rude  approximation,  Portland  cem  is  taken  as  weighing  100  Ibs, 
nat  cem  75  Ibs,  per  cu  ft. 

Packages. 

50.  Owing  to  variations  in  the  specific   gravity  of  cems,  there  is  corre- 
sponding variation  in  sizes  and  weights  of  packages  and  their  contents. 
The  trade  practice  is  to  sell  a  bbl  of  Portland  cem  as  400  Ibs  gross  (including 
wt  of  bbl);  nat,  300  Ibs  gross. 

51.  A  Portland  Cement  barrel  is  2  to  2.2  ft  high,  betw  heads, 
1.38  to  1.46  ft  av  diam.     It  weighs  21  to  29  Ibs,  and  is  lined  with  paper  for 
ordinary  transportation.     Its  capacity  is  3.1  to  3.5  cu  ft,  but  the  cem,  com- 
pressed into  it,  in  packing,  occupies  3.75  to  4.3  cu  ft  loose,  and  weighs  370 
to  390  Ibs.     The  bbl  is  not  returnable. 

52.  A  natural  cement  barrel  weighs  about  20  Ibs.     In  the  Wes- 
tern states  it  contains  265  Ibs;  in  the  Eastern  states,  300  Ibs,  of  cem. 

53.  "  Domestic ""  barrels  are  used  for  shipment  to  all  points  in  the 
U.  S.,  with  slight  reinforcement  for  Gulf  ports;  "standard  export" 
bbls    for    Mexico    and    the  West  Indies;  "'special  export  barrels" 
where  specially  severe  treatment  is  expected. 

54.  The  standard  export  barrel  is    of    better    stock    than    the 
"domestic,"  and  is  reinforced  with  cross  pieces  in  the  heads  and  with  two 
iron  hoops.     It  costs  from  5  to  10  cts  more  than  the  "domestic"  bbl,  vary- 
ing with  cost  of  cooperage  stock. 

55.  The  special  export  barrel    costs  10  to  15  cts  more  than  the 
standard  export  bbl.      It  is  all-hardwood,  heavily  hooped  and  reinforced, 
with  wood  cross-pieces  in  the  heads,  iron  hoops,  and  clamps  to  hold  the 
heads  in  place.     A  heavy  waterproof  lining  is  used  instead  of  the  heavy 
Manila  paper  used  with  the  standard  export  bbl. 

56.  Most  cem  is  now  packed  in  "cloth"  or  paper  bags,  except  for  ship- 
ment by  sea. 

57.  Cement  bag's  are  made  of  cloth  (canvas  or  cotton  duck)   and  of 
"rope   Manila"    paper.     When   empty,  they  measure   about    17  X  28  ins. 
(See  Digest  of  specification  of  the  Am  Soc  for  Testing  Materials.)     A  "cloth" 
bag  is  usually  charged  to  the  purchaser  at  about  10  cts,  and  credited  at 
about  7.5  cts  when  returned.     I'aper  bags  are  charged  at  2.5  cts  each 
and  are  not  returnable. 

58.  The  use  of  paper  bags  obviates  loss  of  time  in  emptying  and  re- 
turning bags,  shortage  on  lost  or  damaged  bags,  and  loss  of  cem  in  transit 
or  by  failure  to  empty  bags  completely;  but  paper  bags  are  more  likely  to 
lose  their  entire  contents  by  breakage,  and  pieces  of  broken  bags  may  get 
into  the  work  and  weaken  it. 

59.  p\>r   large   work,  cem   has  frequently  been  shipped  in  cars    in 
built .  with  little  loss  or  damage,  provided  the  cars  are  carefully  selected. 
This  method  is  especially  advantageous  where  the  cem  is  tested  at  the  mill, 
stored  in  "accepted  bins,"  and  shipped  direct  to  the  work,  in  sealed  cars. 
The  cars  may  be  unloaded  by  automatic  conveyors.     Bags  and  bbls  are 
often  preferred  as  furnishing  a  convenient  means  for  keeping  account  of  the 
quantities  of  cem  entering  the  work;  but,  in  large  operations,  there  should 
be  no  difficulty  in  arranging  to  keep  such  accounts  with  bulk  shipments. 

Age. 

«O.  "Aging"  consists  in  the  slaking  pf  the  free  lime  remaining  in  the 
cem  after  burning.     Good  Portland  cem  is  improved  by  a  few  weeks  of 


936  CEMENT   MORTAR. 

aging  in  dry  air;  and,  if  kept  dry.  it  deteriorates  but  slowly  under  even 
long  storage;  but  nat  cems  usually  suffer  by  aeration;  and  cems  in  general, 
being  composed  of  compounds  with  a  strong  affinity  for  water,  deteriorate 
if  exposed  to  dampness.  Hence,  protection  from  moisture,  even  that  of 
the  air,  is  very  essential  for  the  preservation  of  cems,  as  well  as  of  quick- 
lime. With  this  precaution,  the  cern,  altho  it  may  require  more  time  to 
set,  than  when  fresher,  does  not  otherwise  very  appreciably  deteriorate  in 
many  months. 

61.  Storage,  under  pressure,  tends  to  the  caking  of  cems,  which,  there- 
fore, does  not  necessarily  indicate  deterioration. 

62.  Restoration  by  reburning.     Cems  which  have  deteriorated  by 
exposure,  may  be  in  great  measure  restored  by  reheating  to  redness. 

63.  If  cem  is  stored  in  warm  places,  it  is  apt  to  "flash"  when 
mixed  with  water,  i.  e.,  to  set  much  more  rapidly  than  it  should. 

Testing. 

See  Digests  of  Specifications,  A  S  C  E,  p  942  ;  Engng  Standards  Comm 
of  Gt  Brit,  p  940;  Report  of  Board  of  U  S  Engr  Officers,  p  937. 

64.  Thorq  chemical  tests  of  cem  can   of  course   be  made  only   by 
expert  chemists;  but  the  following  simple  test  may  be  made  by  the  engi- 
neer.    Treated  with  hydrochloric  acid,  "pure  Port  cem  effervesces  slightly, 
gives  off  some  pungent  gas,  and  gradually  forms  a  bright  yellow  jelly,  with- 
out sediment.     Powdered  limestone  or  cem  rock,   mixed  with   the  cem, 
causes  violent  effervescence,  the  acid  giving  off  strong  fumes  until  all  the 
lime  carbonate  is  decomposed,  when  the  yellow  jelly  forms.     Quartz  sand 
remains  undissolved.     Reject  cem  containing  these  adulterants."     Judson, 
"City  Roads  and  Pavements."     The  presence  of  slag  is  generally  indicated 
by  the  sulfur  present,  which  causes  a  milky  appearance,  if  the  cem  be  agi- 
tated in  a  solution  of  hydrochloric  acid  in  water. 

65.  Fuller  and  Thompson   found  that   cems,  which  failed  to  stand  this 
test,  failed  also  to  set  properly;  while  cems   which   passed  it,  also  passed 
more  elaborate  chemical  tests.     (Trans  A  S  C  E,  Vol  59,  '07,  Dec,  pp  73-4.) 


CEMENT.  937 

Properties  and  Tests  of  Cement.  Report  of  Board  U.  S.  A. 
Kngineer  Officers.  Properties  and  tests  of  Portland,  Natural  and  Puz- 
zolan*  cements.  Digest  of  a  Report  of  Majors  W.  L.  Marshall  and  Smith  S. 
Leach  and  Capt.  Spencer  Cosby,  Board  of  Engineer  Officers,  on  testing  Hydraulic 
Cements.  Professional  Papers,  No.  28,  Corps  of  Engineers,  U.  S.  A.,  1901. 

Unfortunately,  tests  for  acceptance  or  rejection  must  be  made  on  a  product 
which  has  not  reached  its  final  stage.  A  cement,  when  incorporated  in  masonry, 
undergoes  chemical  changes  for  months,  whereas  it  is  seldom  possible  to 
continue  tests  for  more  than  a  few  weeks  at  the  most. 

A  few  tests,  carefully  made,  are  more  valuable  than  many,  made  with  less  care. 

Cement  which  has  been  in  storage  for  a  long  time  should  be  carefully 
tested  before  use,  in  order  to  detect  deterioration. 

A  cement  should  be  rejected,  without  regard  to  the  proportion  of  failures 
among  samples  tested,  if  the  samples  show  dangerous  variation  in  quality  or 
lack  of  care  in  manufacture,  and  resulting  lack  of  uniformity  in  the  product. 

The  practice  of  offering  a  bonus  for  cement  showing  an  abnormal  strength 
is  objectionable,  as  it  leads  to  the  production  of  cements  with  defects  not 
easily  detected. 

For  Portland  or  Puzzolan  cement,  make  tests  for  (1)  fineness  of  grinding ;  (2) 
specific  gravity  ;  (3)  soundness,  or  constancy  of  volume  in  setting;  (4)  time  of 
setting,  and  (5)  tensile  strength.  For  Natural  cement*  omit  tests  (2)  and  (3). 

(1)  Fineness.    Ceinentitious  quality  resides  principally,  if  not  wholly,  in 
the  very  finely  ground  particles.    Use  a  No.  100  sieve,  woven  from  brass  wire 
No.  40  Stubs  gage;  sift  until  cement  ceases  to  pass  through.     The  percentage 
that  has  passed  through  is  determined  by  weighing  the  residue  on  the  sieve. 
The  screen  should  be  frequently  examined  to  see  that  no  wires  have  been 
'displaced. 

(2)  Specific  gravity.    The  specific  gravity  test  is  of  value  in  determining 
whether  a  Portland  cement  is  unadulterated.     The  higher  the  burning,  short  of 
vitrification,  the  better  the  cement  and  the  higher  the  specific  gravity.    If  under- 
burned,  the  specific  gravity  of  Portland  cement  may  fall  below  3  ;  if  overturned, 
it  may  reach  3.5.    Natural  cement  has  a  specific  gravity  of  about  2.5  to  2.8,  and 
Puzzolan  about  2.7  to  2.8. 

The  temperature  may  vary  between  60°  and  80°  F.  Any  approved  form  of 
volumenometer  or  specific  gravity  bottle  may  be  used,  graduated  to  cubic  centi- 
meters with  decimal  subdivisions.  Fill  the  instrument  to  zero  of  scale  with 
benzine.  Take  100  grams  of  sifted  cement  that  has  been  previously  dried  by 
exposure  on  a  metal  plate  for  20  minutes  to  a  dry  heat  of  212°  F.,  and  allow  it  to 
pass  slowly  into  the  benzine,  taking  care  that  the  powder  does  not  stick  to  the 
sides  of  the  graduated  tube  above  the  fluid,  and  that  the  funnel,  through  which 
it  is  introduced,  does  not  touch  the  fluid.  The  approximate  specific  gravity  will 
be  represented  by  100  divided  by  the  displacement  in  cubic  centimeters.  The 
operation  requires  care. 

(3)  Soundness,  and  (4)  setting  qualities.    The  temperature  should 
not  vary  more  than  10°  from  62°  F.     For  Portland  cement  use  20,  for  Natural  30, 
and  for  Puzzolan  18  per  cent,  of  water  by  weight.     Mix  thoroughly  for  5  minutes. 
On  glass  plates  make  two  cakes  about  3  inches  in  diameter,  %  inch  thick  at  the 
middle  and  drawn  to  thin  edges,  and  cover  them  with  a  damp  cloth.    At  the  end 
of  the  minimum  time  specified  for  initial  set,  apply  needle  J^-  inch  diameter, 
weighted  to  \£  pound.     If  an  indentation  is  made,  the  cement  passes  the  require- 
ment for  initial  setting.     Otherwise  the  setting  is  too  rapid.    At  the  end  of  the 
maximum  time  specified  for  final  set,  apply  the  needle  ^V  inch  diameter,  loaded 
to  one  pound.    If  no  indentation  is  made,  the  cement  passes  the  requirement  for 
final  set.     Otherwise  the  setting  is  too  slow. 

Generally  speaking,  both  periods  of  set  are  lengthened  by  increase  of  moisture, 
and  shortened  by  increase  of  temperature. 

*By  Portland  cement,  in  this  report,  is  meant  the  product  obtained  by 
calcining  intimate  mixtures,  either  natural  or  artificial,  of  argillaceous  and 
calcareous  substances,  up  to  incipient  fusion.  By  Natural  cement  is  meant 
one  made  by  calcining  natural  rock  at  a  heat  below  incipient  fusion,  and  grind- 
ing the  product  to  powder.  By  Puzzolan  is  meant  the  product  obtained  by 
grinding  slag  and  slaked  lime,  without  subsequent  calcination. 

62 


938  CEMENT   MOETAR. 

Recommendations  of  Board  of  II.  S.  A.  Engineer 
Officers.     Continued. 

In  gaging  Portland  cement  in  damp  weather,  thesamples  should  be  thoroughly 
dried  before  adding  water.  This  precaution  is  not  deemed  necessary  with 
Natural  cement.  Sufficient  uniformity  of  temperature  will  result  if  the  testing 
room  be  comfortably  warmed  in  winter,  and  if  the  specimens  be  kept  out  of  the 
Bun  in  a  cool  room  in  summer,  and  under  a  damp  cloth  until  set.  Temperatures 
may  vary  between  60°  and  80°  F.,  without  affecting  results  more  than  the 
probable  error  in  the  observation. 

Boiling  test.  Place  the  two  cakes  under  a  damp  cloth  for  24  hours.  Place 
one  of  them,  still  attached  to  its  plate,  in  water  28  days;  immerse  the  other  in 
water  at  about  70°  F.,  and  let  it  be  in  a  rack  above  the  bottom  of  the  receptacle; 
heat  the  water  gradually  to  the  boiling  point,  maintain  the  heat  for  6  hours  and 
then  let  cool.  The  boiled  cake  should  not  warp  or  become  detached  from  the 
plate,  or  show  expansion  cracks.  If  the  cold-water  cake  shows  evidences  only 
of  swelling,  the  cement  may  be  used  in  ordinary  work  in  air  or  fresh  water  for 
lean  mixtures,  but  if  distortion  or  expansion  cracks  appear  in  it,  the  cement 
should  be  rejected. 

Accelerated  tests  are  not  generally  recommended,  but  where  a  test  mugt 
be  made  in  a  short  time,  the  boiling  test  is  considered  about  the  best.  It  not 
only  gives  short-time  indications,  but  at  once  directs  attention  to  the  presence 
of  ingredients  which  might  lead  to  disintegration.  On  the  other  hand,  it  may 
lead  to  the  rejection  of  a  cement  which  would  behave  satisfactorily  in  actual 
work  alid  which  would  stand  the  test  after  air-slaking.  Sulphate  of  lime,  while 
enabling  cements  to  pass  the  boiling  tests,  introduces  an  element  of  danger. 

(5)  Tensile  tests  are  preferred  to  flexural  or  compressive  tests.      Sand  • 
tests  are  the  more  important  and  should  always  be  made;  and  neat  tests  should 
be  made  if  time  permits. 

A  cement  which  tests  moderately  high  at  7  days,  and  shows  a  substantial 
increase  in  strength  in  28  days,  is  more  likely  to  reach  the  maximum  strength 
slowly  and  retain  it  indefinitely  with  a  low  modulus  of  elasticity,  than  a  cement 
which  tests  abnormally  high  at  7  days  with  little  or  no  increase  at.  28  days. 

Use  briquettes  of  the  form  recommended  by  the  American  Society  of  Civil 
Engineers,*  measuring  1  inch  square  in  cross-section  at  place  of  rupture,  and 
held  by  close-fitting  metal  clips,  without  rubber  or  other  yielding  contacts.  The 
tests  should  be  made  immediately  after  taking  the  briquettes  from  the  water. 

Neat  tensile  tests.  Use  unsifted  cements.  For  Portland  cement,  use 
20;  for  Natural,  30;  and  for  Puzzolan,  18  per  cent,  water  by  weight.  Place  the 
cement  on  a  smooth  non-absorbent  slab ;  in  the  middle  make  a  crater  sufficient,  to 
hold  the  water;  add  nearly  all  the  water  at  once,  the  remainder  as  needed  ;  mix 
thoroughly  by  turning  with  the  trowel,  and  vigorously  rub  or  work  the  cement 
for  5  minutes. 

Place  the  briquette  mold  on  a  glass  or  slate  slab.  Fill  the  mold  with  consecu- 
tive layers  of  cement,  each  to  be  %  inch  thick  when  rammed.  Give  each  layer 
30  taps  with  a  soft  brass  or  copper  rammer  weighing  1  pound,  having  a  face  % 
inch  diameter  or  0.7  inch  square,  and  falling  about  %  inch. 

After  filling  the  mold  and  ramming  the  last  layer,  strike  smooth  with  a  trowel, 
tap  mold  lightly  or^side,  to  free  cement  from  plate,  remove  the  plate,  and  leave 
for  24  hours,  covered  with  a  damp  cloth.  Then  remove  the  briquette  from  the 
mold  and  immerse  it  in  freshwater,  which  should  be  renewed  either  continu- 
ously or  twice  in  each  week  during  the  specified  time. 

Tensile  tests  with  sand.  For  Portland  and  Puzzolan  cements,  use  \ 
part  cement  to  3  parts  sand  ;  for  Natural  or  Rosendale,  1  to  1.  Use  crushed 
quartz  sand,  passing  a  No.  20  standard  sieve,  and  being  retained  on  a  No.  30 
standard  sieve. 

After  weighing  carefully,  mix  dry  the  cement  and  sand  until  the  mixture  is 
uniform,  add  the  water  as  in  neat  mixtures,  and  mix  for  5  minutes.  The  con- 
stituents should  be  well  rubbed  together. 

For  maximum  strength  in  tested  briquettes,  Portland  cements  require 
water  =  11  to  12%  per  cent,  by  weight  of  constituent  sand  and  cement ; 
Natural,  15  to  17 ;  and  Puzzolan,  9  to  10. 

A  machine  which  applies  the  stress  automatically  and  at  a  uniform  rate 

*  See  page  944. 


CEMENT.  939 

Recommendations  of  Board  of  U.  Is.  A.  Engineer 
Officers.     Continued. 

of  increase  is  preferable  to  one  controlled  entirely  by  hand.  The  stress 
should  be  increased  at  the  rate  of  about  400  fos.  per  minute.  A  rate  materially 
greater  or  less  than  this  will  give  different  results. 

The  highest  tensile  strength  from  each  set  of  briquettes  made  at  any  one  time 
is  to  be  considered  the  governing  test. 

Field  tests  are  recommended,  whether  or  not  the  more  elaborate  tests 
above  described  have  been  made.  In  connection  with  tests  of  weight  and  fine- 
ness, and  observations  of  texture  and  hardness  in  the  work,  field  tests  often 
suffice  for  well-known  brands,  showing  whether  the  cement  is  genuine  and 
whether  it  is  reasonably  sound  and  active.  Pats  and  balls  of  neat  cement  from 
the  storehouse,  and  of  mortar  from  the  mixing  platform  or  machine,  should  be 
frequently  made.  Estimate  roughly  the  setting  and  hardening  qualities  by 
pressure  of  the  thumb-nail ;  hardness  of  set  and  strength  by  breaking  with  the 
hand  and  by  dropping  upon  a  hard  surface.  The  boiling  test  may  also  be  used. 
Should  the  simple  tests  give  unsatisfactory  or  suspicious  results,  then  a  full  series 
of  tests  should  be  carefully  made. 

A  cement  may  be  rejected  if  it  fails  to  meet  any  of  the  following  requirements 

Requirements. 

Portland.    Natural.    Puzzolan. 
Slow.    Quick. 
Fineness.    Percentage  to  pass  through  a  No. 

100  sieve  as  in  (1) 87  to  92*  80  97 

Specific  gravity.    Between 3.10  3.10      Not  2.7 

and  3.25  3.25     given  2.8 

Time  of  setting.    Initial,  not  less  than 45m.         20m.    20m.  45m. 

nor  more  than 30  m 

Final,  not  less  than 45m 

nor  more  than   10  h.  2.5  h.     4  h.  10  h. 

Tensile  strength,  neat, 

-  /   7  days  f 450  400  90  350 

fts.  per  sq.  in.  -j  2g  da-y^ 54Q  m         m  500 

Tensile  strength.      With  sand,  as  in    (5). 

fcsnprsnii  i   7  days  f 140  120  60  140 

1 28  days  f 220  180          150  220 

*92  per  cent,  is  quite  commonly  attained  by  high-grade  American  Portlands, 
but  rarely  by  imported  brands.     For  the  latter,  use  87. 
f  Reject  any  cement  not  showing  an  increase  at  28  days  over  7  days. 


940  CEMENT   MORTAR. 

DIGESTS  OF  SPECIFICATIONS. 

Requirements. 
American  Society  for  Testing  Materials. 

Digest  of  Specification  adopted   by   the   Society,   Nov   14,   1904. 
See  Amendments  of  1908.* 

Adopted  by  Assn  of  Am  Portland  Cement   Mfrs,  June  10, 

1904,*  and  by  Am  Ry  Eng  «fc   .Mainl   of  Way  Assn,  Mar  21,  1905.* 

1.  Packages.     Brand  and  mfr's  name  plainly  marked  thereon.     Bag 
to  contain  94  Ibs  net.     Bbl  Portland  =  4  bags;  nat,  3  bags. 

2.  Tests  in  accordance  with  recommendations  of  Comm  of  A  S  C  E,  p 
942.     "Gem,  failing  to  meet  the  7-day  requirements,  may  be  held  awaiting 
the  results  of  the  28-day  tests  before  rejection." 

3.  Qualities.  Natural  Portland 

Sp  gr,  cem  thoroly  dried  at  100°  C.* min     2.8  *  min    3.1 

Loss  of  wt,  on  ignition ...  * 

Fineness.     Percentage,  by  wt: 

Residue  on  No.  100  sieve max    10  max      8 

on  No.  200  sieve max    30  max    25 

Time  of  setting,  mins,  initial min     10  min     30 


hard 


min     30  /  min     60 


•    L  max  180  \  max  600 

Tensile  strgth, 

Min  requirements,*  Ibs  per  sq  inch;   briquettes  1  inch  square  section. 
Briquettes    must    show    no    retrogression    in    strgth    during    specified 

periods. 

1  day  in  moist  air  in  all  cases. 
Neat  Natural  Portland 

24  hours 50  to  100  150  to  200 

7  days 100  to  200  450  to  550 

28  days 200  to  300  550  to  650 

1  part  cem,  3  parts  standard  sand. 

7  days 25  to    75  150  to  200 

28  days 75  to  150  200  to  300 

Soundness  (constancy  of  volume) 

(For  normal  and  accelerated  tests,  see 

digest  of  A  S  C  E  Specfns,  p  945) to  stand  to    stand 

normal  test.  normal  and 

accelerated 
tests. 

Anhydrous  sulfuric  acid max  1 .75% 

Magnesia max  4.00% 


Engineering  Standards  Committee  of  Great  Britain, 

Adopted  Nov.  23,  1904. 

1.  Consignments  of  from  100  to  250  tons  to  have  expert  testing  and 
chemical  analysis.     For  consignments  of  less  than  100  tons,  makers  shall,  if 
required,  give  certificate,  for  each  delivery,  that  cem  meets  this  spec'n. 

2.  Samples.     Test  samples  to  be  taken  as  soon  as  bulked  at  factory 
or  on  the  work,   at  consumer's  option.     Samples  to   be   taken   from  each 
"parcel,"  each  sample  consisting  of  cem  from  at  least  12  diff  positions  in 
same  "heap,"  mixed  together  and  spread  out,  3  ins  deep,  for  24  hours,  at  a 
temp  between  58°  and  64°  F. 

*  Amendments  adopted  by  Am  Soc  for  Testing  Materials,  Sep  1908: 

Strength.  The  means  of  the  values  given  shall  be  taken  as  the 
required  minima  where  these  are  not  specified. 

Natural  Cement.     Omit  specification  for  specific  gravity. 

Portland  Cement.  Specific  gravity.  For  "thoroly  dried  at  100°  C," 
read  "ignited  at  a  low  red  heat." 

Loss  of  weight,  on  ignition,  >  4  %. 


TESTS. 


941 


Requirements.     Engineering  Standards  Committee  of 
Crreat  Britain.     Continued. 

3.  Fineness. 

Meshes 

«  Wire  Residue  not 

per  lin  inch         per  sq  inch  diam,  ina  to  exceed 

76  5,776  0.0044  5.0% 

180  32,400  0.0018  22.5% 

Wire  woven,  not  twilled. 

4.  Tensile  strength. 

Test  room  temperature,  58Q  to  64°  F. 

Water,  fresh,  renewed  every  7  days.     Temp  58°  to  64°  F. 

Paste,  smooth,  easily  worked,  that  will  leave  the  trowel  cleanly  in  a  com- 
pact mass. 

Briquette,  filled,  not  rammed,  into  mold  resting  upon  an  iron  plate,  and 
left  until  cem  has  set.  Briquette  kept  in  damp  atmosphere  24  hours;  then 
in  water  until  broken.  Clips.  See  Fig.  1. 


=  0.40  inch; 
=  0.60     " 
=  1.00     " 
=  thickness; 
=  1.75  inch; 
=  2.00     " 


Fig  1.    Briquet  and  Clips.     British  Standard. 


Load,  start  at  zero.     Add  100  Ihs  each  12  seconds. 

Neat  test.     6  briquettes  at  7  days,  and  6  at  28  days.     Av  of  the  six  ac- 
cepted as  the  tensile  strgth  of  the  cement.     7  days,  <  400  Ibs  per  sq.  inch- 
28  days,  <  500. 

When  7  day  test  is  betw  Increase,  from  7  to  28  days, 

must  be   not  less  than 
400  and  450   IDS  per  sq.  in  .....................  25  per  cent. 

450  and  500      "     "     "     "  ....................  20 

500  and  550      "     "     "     "  ....................  15 

550  and  over    "     "     "     "  ....................  10        " 


Test  with  sand.  By  wt,  1  cem,  3  standard  sand  from  Leighton  Buzzard, 
thoroly  washed  and  dried.  Sand  must  pass  No.  20  sieve  of  0.0164  inch 
wire,  and  remain  on  No.  30  sieve  of  0.0108  inch  wire.  Mixture  thoroly 
wetted,  but  without  superfluous  water.  7  days,  120  Ibs  per  sq  inch;  28 
days,  225.  Increase,  from  7  to  28  days,  not  less  than  20  %. 


942  CEMENT   MORTAR. 

Requirements.     Engineering  Standards  Committee  of 
Great  Britain.     Continued. 

1    Sot  I  in-  •     Time'  mins-   • 

o.  »<       ing1.  maximum  minimum 

Quick 30  10 

Medium 120  30 

Slow 300  120 

"Set"  has  occurred  when  needle,  loaded  with  2%  Ibs,  with  flat  end  Vio 
inch  square,  fails  to  make  an  impression. 

6.  Soundness.     LeChatelier  test.      Expansion    not  to  exceed  12  mm 
after  24  hours  aeration;  6  mm  after  7  days. 

7.  Specific  gravity.     Not  less  than  3.15,  when  sampled  and  hermeti- 
cally sealed  at  makers'.     Not  less  than  3.10,  when  sampled  after  delivery  to 
consumer. 

8.  Analysis. 

Water,  >  2  %,  whether  added  or  naturally  absorbed  from  the  air. 

Calcium  sulfate,  >  2  %  of  wt  of  cem,  calculated  as  anhydrous  calcium 
sulfate. 

Lime,  >  enough  to  saturate  the  silica  and  alumina. 

Insoluble  residue,  >  1.5  %.  Magnesia,  >  3  %.  Sulfuric  an- 
hydride, >  2.5  % 


Tests. 
American  Society  of  Civil  Engineers. 

Digest  of  report  of  Committee  on  Uniform  Tests  of  Cement,*  Jan  '03.  as 
amended  Jan  '04  and  Jan  '08. 

1.  Selection  of  samples  left  to  discretion  of  engineer.     Number  of 
samples  and  quantity  to  be  taken  from  each  package  depend  upon  impor- 
tance of  work,  upon  number  of  tests  to  be  made  and  upon  facilities  for 
making  them.     Where  conditions  permit,  sample  one  bbl  in  ten.     Individual 
samples  may  be  mixed,  and  av  tested;    but,  where  time  permits,  test  sepa- 
rately. 

2.  Barreled  cement  to  be  sampled  through  a  hole  made  in  the  center 
of  a  stave,  midway  between  the  heads,  or  in  the  head.     Bagged  cement  to 
be  sampled  from  surface  to  center. 

3.  Samples  to  be  coarsely  screened  thru  a  No.  20  sieve. 

4.  Chemical  analysis  may  show  adulteration  in  the  case  of  cems 
rich  in  inert  material,  but  is  not  conclusive  evidence  of  quality.     Committee 
recommends  method  proposed  by  Committee  on  Uniformity  &c.,  New  York 
Section  of  the  Society  for  Chemical  Industry,  see  E  N,  '03,  Jul  16,  p  60; 
ER, '03,  Julll,p49. 

5.  Specific  gravity  test.    Le  Chatelier's  method  recommended.    Fig  1. 
Flask,  D,  120  cubic  centimeters  (cc);  neck  about  9  mm  diam  and  20  cm 

long,  with  bulb,  C;  vol,  betw  marks,  F  and  E,  20  cc.  Neck  graduated,  to  0.1 
cc,  above  F.  Neck  of  funnel,  B,  enters  neck  of  flask,  and  extends  to  top  of 
bulb,  C.  Use  benzine  (62°  Baume  naphtha)  or  kerosene  free  from  water. 
During  the  operation,  in  order  to  avoid  variations  in  the  temperature  of 
this  liquid,  the  flask  is  kept  immersed  in  water,  in  a  jar.  Two  methods,  viz-. 

(a)  Flask  filled  to  lower  mark,  E.     Weigh  out  64  grams  (2.25  oz)  of  the 
cem  powder,  cooled  to  temp  of  liquid.     Thru  the  funnel,  B,  introduce  the 
cem  powder  gradually  until  surf  of  liquid  reaches  the  upper  mark,  F.     Then 
64  grams,  minus  wt  of  powder  remaining  unused,  =  wt,  w,  which  has  dis- 
placed 20  cc  and 

Specific  gravity  =  w  /  20. 

(b)  Fill,  with  liquid,  to  lower  mark,  E,  as  before.     Add  the  entire  64 
grams  cem  powder,  liquid  rising  to  some  division  of  the  graduated  neck. 

*Geo.  S  Webster,  Richard  L.  Humphrey.  Geo.  F.  Swain.  Alfred  Noble, 
Louis  C.  Sabin,  Spencer  B.  Newberry,  Clifford  Richardson,  F.  H.  Lewis, 
W.  B.  W.  Howe.  A  S  C  E,  Proceedings,  Jan  '03,  Feb  '04,  Feb  '0* 


TESTS. 


943 


Tests.     Am  Soc  Civ  Eng-rs.     Continued. 

The  reading  of  this  division,  plus  20  cc,  is  the  vol,  v,  displaced  by  64  grams 
of  the  powder;  and 

Specific  gravity   =  64  /v. 

6.  Fineness.  Sieves  should  be  circular  about  20  cm  (7.87  ins)  diam, 
6  cm  (2.36  ins)  high,  with  pan  5  cm  (1.97  ins)  deep,  and  a  cover. 

Sieves  should  be  of  wire  cloth, 

No.  100,    96  to  100  meshes  per  lineal  inch;  wire  0.0045  inch  diam. 

No.  200,  188  to  200        "       "          "         "          "   0.0024    " 

Use  50  grams  (1.76  oz)  or  100  grams,  cem;  dried  at  100°  C  (212°  F). 
Hand  sieving  preferred.  Use  No.  200  sieve  until  one  minute  continuous 
sieving,  at  about  200  strokes  per  minute,  passes  not  more  than  0.1  %.  Weigh 
residue,  and  treat  it  similarly  on  No.  100  sieve.  A  small  quantity  of  large 
steel  shot,  placed  in  the  sieve,  expedites  the  work.  The  results  should  be 
reported  to  the  nearest  0.1  %. 


Fig  1. 

Sp  grav  Flask. 


Fig  2. 

Vicat  Needle  Apparatus. 


7.  Xormal  consistency.  The  percentage  of  water,  used  in  making 
the  pastes,  for  tests  of  strgth,  soundness  and  setting,  vitally  affects  the 
results.  Normal  consistency  is  determined  as  follows  : 

The  quantity  of  cem,  to  be  subsequently  used  for  each  batch  in  making 
the  briquettes,  but  not  less  than  500  grams,  is  kneaded  into  a  paste  as  under 
"Mixing,"  ^  12,  quickly  formed  into  a  ball,  with  the  hands,  and  tossed 
six  times  from  hand  to  hand,  held  6  ins  apart.  The  ball  is  then  pressed  thru 
the  larger  opening  of  the  Vicat  needle  apparatus  into  the  gum  ring,  I,  7  cm 
(2.76  ins)  diam,  4  cm  (1.57  ins)  deep,  smoothed  off  below,  and  placed  on  the 
glass  plate,  J.  Its  upper  surf  is  then  smoothed  off  with  a  trowel.  The  point 
of  the  Vicat  needle,  H,  is  then  brought  into  contact  with  the  upper  surf  of  the 
sample,  and  the  cyl,  L,  is  allowed  to  descend.  The  paste  is  of  the  normal  con- 
sistency when  the  needle  penetrates  to  a  depth  of  1  cm  (0.39  in).  With  this 
rather  wet  paste,  the  committee  believes  that  variations,  in  the  amount  of 
compression  to  which  the  briquette  is  subjected  in  molding,  are  likely  to  be 
less  than  with  a  drier  paste. 

H.  Setting.  Vicat  needle,  H,  Fig  2,  1  mm  (0.039  in)  diam,  loaded  to  300 
grams  (10.58  oz).  Setting  has  begun  when  needle  ceases  to  pass  a  point  5 
mm  (0.20  in)  above  the  upper  surface  of  the  glass  plate;  and  has  terminated 
when  the  needle  does  not  visibly  penetrate  the  mass.  Test  pieces  kept  damp, 
during  test,  by  storage  in  a  moist  box  or  closet,  or  placed  on  a  rack  over  water 
in  a  pan  and  covered  by  a  damp  cloth,  the  cloth  resting  upon  a  wire  screen,  so 
as  not  to  touch  the  test  pieces.  Keep  needle  clean;  as  cem,  adhering,  seriously 


944 


CEMENT   MORTAR. 


Tests.    Am  Soc  Civ  Engrs.    Continued. 

vitiates  results.  Time  of  setting  is  materially  affected  by  temp  of  mixing 
water,  by  temp  and  humidity  of  air,  by  the  percentage  of  water  used,  and  by 
the  amount  of  molding  paste  receives. 

9.  Standard  sand.  Crushed  quartz  objectionable,  "especially  on  ac- 
count of  its  high  percentage  of  voids,  the  difficulty  of  compacting  in  the 
molds,  and  its  lack  of  uniformity."  Comm  recommends  natural  sand  from 
Ottawa,  111.  Sand  to  pass  a  No.  20  sieve,  with  wire  diam  =  half  the  diam  of 
spaces  betw  wires;  <  99  %  to  be  retained  on  a  similar  No.  30  sieve  after  1 
minute  of  continuous  sifting  of  a  500  gram  sample.  The  Sandusky  Portland 
Cement  Co.,  Sandusky,  O.,  has  agreed  to  furnish  such  a  sand  at  actual  cost 
of  preparation. 

1O.  Standard  briquette.  See  Fig.  3.  Am  Soc  Civ  Engrs.  Dotted 
lines  are  those  recommended  by  earlier  Comm.  Trans,  Vol  14,  Nov.  1885. 


W  =  1.25  ins. 
c     =  0.25  " 
=  contact 
with 
briquet. 


Fig  3.     Briquet. 


Fig  5.     Clip. 


Fig  4. 

ing  Mold. 


Gang 


11.  Molds,  "of  brass, bronze  or  some  equally  non-corrodible  material;" 
sides  strong  enough  to  resist  spreading.     Gang  mold,  Fig  4,  recommended, 
because  the  greater  quantity  of  mortar,  required  for  it,  conduces  to  uniform- 
ity of  results.     Molds  to  be  "wiped  with  an  oily  cloth  before  using." 

12.  Mixing.     Proportions  stated  by  wt;  quantity  of  water  stated  as 
percentage  of  dry  material. 

Metric  system  recommended. 

Temp  of  room  and  mixing  water  as  near  21°  C  (70°  F)  as  practicable. 

Sand  and  cem  thoroly  mixed  dry.  Mixing  done  on  some  non-absorbing 
surf,  preferably  plate  glass.  If  an  absorbing  surf  is  used,  it  should  first  be 
thoroly  dampened. 

Quantity  of  material,  mixed  at  one  time,  depends  on  number  of  test 
pieces  to  be  made;  about  1000  grams  (35.28  oz.)  convenient  to  mix,  espe- 
cially by  hand  methods. 

Hand  mixing  and  hand  molding  recommended.  Material  weighed,  and 
placed  on  mixing  table,  and  a  crater  formed  in  the  center,  into  which  the 
proper  percentage  of  clean  water  is  poured;  material  on  outer  edge  turned 
into  crater  by  aid  of  a  trowel.  As  soon  as  the  water  is  absorbed,  the  opera- 
tion is  completed  by  vigorously  kneading  with  the  hands  for  an  additional 
1  ^  minutes.  A  sand-glass  affords  a  convenient  guide  for  the  time  of  knead- 
ing. The  hands  should  be  protected  by  gloves,  preferably  of  rubber. 

Molds  filled  immediately  after  the  mixing  is  completed,  material  pressed 
in  firmly  with  the  fingers  and  smoothed  off  with  a  trowel,  without  mechani- 
cal ramming;  material  heaped  up  on  the  upper  surface  of  the  mold.  In 
smoothing  off,  the  trowel  should  be  drawn  over  the  mold,  exerting  a  mod- 
erate pressure  on  the  excess  material.  Mold  turned  over  and  operation 
repeated. 


TESTS.  945 

Tests.     Am  Soc  Civ  Engrs.     Continued. 

Weigh  the  briquettes  "just  prior  to  immersion,  or  upon  removal  from  the 
moist  closet,"  and  reject  those  varying  >  3  %  from  the  av. 

13.  Moist  Closet.     "A  moist  closet  consists  of  a  soapstone  or  slate  box, 
or  a  metal-lined  wooden  box — the  metal  lining  being  covered  with  felt  and 
this  felt  kept  wet.     The  bottom  of  the  box  is  so  constructed  as  to  hold  water, 
and  the  sides  are  provided  with  cleats  for  holding  glass  shelves  on  which  to 
place  the  briquettes.     Care  should  be  taken  to  keep  the  air  in  the  closet 
uniformly  moist." 

"Where  a  moist  closet  is  not  available,  a  cloth  may  be  used  and  kept 
uniformly  wet  by  immersing  the  ends  in  water.  The  cloth  should  be  kept 
from  direct  contact  with  the  test  pieces  by  means  of  a  wire  screen  or  some 
similar  arrangement." 

14.  Immersion.     "After  24  hours  in  moist  air  the  test  pieces  for  longer 
periods   of  time   should   be  immersed  in  water    maintained  as  near   21°  C 
(70°  F)  as  practicable;  they  may  be  stored  in  tanks  or  pans,  which  should  be 
of  non-corrodible  material." 

15.  Tensile  strength.    Solid  metal  clip,  Fig.  5,  recommended.     No 
cushioning  between   clip   and   briquette.     Briquettes   broken   immediately 
after  removal  from  water.     Center  the  briquette  carefully  in  the  clip,  to 
avoid  transverse  stresses.     Load  applied  at  rate  of  600  Ibs  per  min.    "The 
average  of  the  briquettes,  of  each  sample  tested,  should  be  taken  as  the  test" 
of  that  sample,  "excluding  any  results  which  are  manifestly  faulty." 

16.  Soundness  (Constancy  of  Volume).     "In  the  present  state 
of  our  knowledge  it  cannot  be  said  that  cement  should  necessarily  be  con- 
demned simply  for  failure  to  pass  the  accelerated  tests  (be'ow);  nor  can  a 
cem  be  considered  entirely  satisfactory,  simply  because  it  has  passed  these 
tests." 

Pats  of  cem  paste  of  normal  consistcy  (^j  7),  abt  7.5  cm  (2.95  ins)  diam, 
1 .25  cm  (0.49  in)  thick  at  center,  tapering  to  thin  edge,  made  on  a  clean  glass 
plate  about  10  cm  (3.94  ins)  square,  24  hours  in  moist  air  before  test. 

(1)  Normal  test.     One  pat  immersed  in  water  maintained  as  near  21°  C 
(70°  F)  as  possible;  one  in  air  at  ordinary  temp.     Both  observed  at  intervals 
for  28  days. 

(2)  Accelerated  test.      A  pat  is  exposed  in  any  convenient  way  in  an 
atmosphere  of  steam,  above  boiling  water,  in  a  loosely  closed  vessel,  for  5 
hours. 

Pats  must  remain  firm  and  hard,  and  show  no  signs  of  cracking,  distortion 
or  disintegration.  Warping  may  be  conveniently  detected  by  applying  a 
straight  edge  to  the  surf  which  was  in  contact  with  the  plate. 


946 


CEMENT   MORTAR. 


Sand.* 

Composition. 

1.  The  sand,*  used  in  mortar,  is  ordinarily  made   up   chiefly  of  grains  of 
quartz  (silica),  with  some  impurities,  mostly  grains  of  silicious  minerals. 
In  testing  cements    in  the  laboratory,  crushed  quartz  or  some    standard 
natural  sand  is  used.     (See  Spec'ns  A  S  C  E,  under  Cement,  p.  942.) 

2.  The  silica  of  the  quartz,  in  sand,  undergoes  no  chemical  change 
in  the  mortar;  but  the  use  of  sand,  by  diminishing  the  quantity  of  cem  reqd, 
reduces  also  the  cost  of  the  finished  work.     See  remarks  on  strength,   under 
Mortar,  p  947  t. 

SIZES  OF   GRAIXS. 

3.  Screening.     Sand  and  gravel  are  screened,  usually  in  an  inclined 
fixed  screen,  upon  which  the  material  is  placed  by  a  conveyor,  or  shoveled 
by  hand;  or  in  an  inclined  revolving  cylindrical  or  hexagonal  screen,  into 
which  the  material  is  fed. 

4.  Method  of  quartering.     "To  obtain  an  average  sample  from 
a  pile  of  sand,  gravel   or  stone,  the  method  of  quartering  is  useful.     Shovel- 
fuls of  the  material  are  taken  from  various  parts  of  the  pile,  mixed  together 
and  spread  in  a  circle.     The  circle  is  quartered,  as  one  would  quarter  a  pie, 
one  Of  the  quarters  is  shoveled  away  from  the  rest,  thoroughly  mixed, 
spread,  and  quartered  as  before.     The  operation  is  repeated  until  the  quan- 
tity is  reduced  to  that  required  for  the  sample."     (T  &  T,  p.  281.) 

Mechanical  Analysis. 

5.  The  mechanical  or  granulometric  analysis    of  sands, 

etc.,  is  the  determination,  in  any  given  sand  or  broken  stone,  of  the  propor- 
tions of  grains  of  diff  sizes.  It  is  usually  performed  by  means  of  sieves  or 
screens.  See  f  3.  Sometimes,  for  broken  stone,  &c.,  by  hand-picking. 

6.  Fig.  1   shows  mechanical  analyses  of  a  gravel  and  a  sand   by  Mr.  Allen 
Hazen  (Mass.  State  Board  of  Health,  Report  1892,  pp.  546-7).     In  order 
to  represent  both  analyses  on  a  single  diagram,  we  have  used  diff  scales  for 
diams  for  the  two  materials. 

7.  In  Fig.  1,  the  diagrams  show,  for  the  two  materials  there  represented, 
that 

of  the  sand,      10  %  was  in  grains  under,  and  90  %  over,    0.055  mm  diam 
"  "    gravel,  10  %    ' "         "    90  %      "      34.5        "       " 


10 


^ 

- 

2.5  | 

2.0  1 

"f 

0.5  § 

o  5 

gr« 

22^ 

— 

m=5l 

^ 

£^ 

34.5 

/ 

7 

/ 

^^ 

^ 

a&- 

^0.055 

-JL 

f^" 

,  —  —  ' 

7»=0 

46 

"0      OD     20     30     40      50     60     70     80     90    100 

fercentage  gassing 
Fig  1.     Sand  Analyses. 


*  By  "  sand "  or  "  gravel "  we  mean  a  mixture  of  mineral  par- 
ticles with  air,  or  water,  or  both;  i.  e.,  an  aggregation  of  mineral  particles, 
with  voids  betw  them  said  voids  being  filled  with  air,  or  with  water,  or 
with  air  and  water,  as  the  case  may  be. 

Hence,  the  "volume"  of  a  given  quantity  of  sand  or  of  gravel  is  the  space 
occupied  by  both  the  solid  particles  and  the  air  or  water  or  both,  filling  the 
voids. 

"Dry  sand,"  or  "dry  gravel,"  means:  not  solid  mineral,  but  a  mixture  of 
dry  particles  of  sand  (or  gravel)  and  dry  air. 

The  solid  mineral  portion  of  such  sand  or  gravel,  we  designate  as  "solid." 


SAND. 


947 


Effective  Size. 

8.  The  effective  size  ("e.  s.")  of  a  sand  or  gravel,  as  defined  by  Mr. 
Hazen  (Mass   State  Board  of  Health,  Report  1892,  p  341;  Hazen,  Filtration, 
pp  21,  240)  is  that  size,  than  which  10  %,  by  wt,  of  the  grains  are  smaller,  and 
90  %  larger.     Or,  the  length  of'  the  ordinate,  at   10   %   passing,  gives  the 
effective  size.     Thus,  in  the  cases  just  mentioned,  Fig  1,  we  have: 

for  the  sand,  e.  s.  =  0.055  mm;     for  the  gravel,  e.  s.  =  34.5  mm. 
Uniformity  Coefficient. 

9.  Uniformity  coefficient.     Similarly,  let  m  =  that  diam  of  grain, 
than  which  60  %,  by  wt,  is  smaller,  while  40  %  is  larger.     In  Fig  1,  we  have 

for  the  sand,      m    =        0.46  millimeters; 

"  gravel,    m    =      51.00 

The  uniformity  coefficient  ("  u.  c.  "),  is  m/e.  s.;  and  we  have: 
for  the  sand,    u.  c.  =    0.46/  0.055      =     8.4; 

"  gravel,  u.  c.  =  51.00/34.5          =      1.48. 

10.  With  m  =  e.  s.,  the  unif  coeff,  u.  c.,  would  have  its  least   possible 
value,    =   1.      In  general  the  less  nearly  uniform  a  sand  is,  as  to  size,  the 
higher  is  its  "uniformity  coeff." 

11.  In  ordinary  bank  sand,  the  effective  size,  e.  s.,  does  not  vary  widely. 
Hence  the  uniformity  coefficient,  u.  c.  =  m/e.  s.,  varies  roughly  with  that 
diam,  m,  than  which  60  %  of  the  grains  are  smaller,  and  thus  serves  as  an 
indication  of  the  coarseness;    as   well   as   of   the   departure   from 
uniformity,  of  the  sand.     (T  &  T,  p.  182.) 

Feret's  Method. 

12.  Mr.  R.  Feret  (Annales  des  Fonts  et  Chaussees,  1892,  second  semes- 
tre,)  made  elaborate  experiments  as  to  the  effects  of  fineness  of  sand,  and 
the  mixture  of  different  finenesses,  upon  the  density,  etc.,  of  sand  and  upon 
different    qualities  of    the    mortar.     He    divided    his    sands    into    three 
finenesses,  as  follows: 

Coarse,     c,  passing  5.0  mm  diam  =       4  meshes  /  sq  cm  =     5  meshes  /  lin  in 
Medium,  m,       "       2.0    "       "       =     36      "        /    "     "    =15       "       /     " 
Fine,         /,        "       0.5    "        "       =  324       "        /    "     "    =  46       "       /     " 
"Coarse"  grains  are  retained  on  2.0  mm  diameter;  "medium"  on  0.5  mm. 


4* 


aO 


"i'e       <*t 

v;< 


Sand  Analyses,  Feret. 
See  U  18. 


'•« 


x 


13.  The  results,  obtained  in  a  certain  case,  with  diff  mixtures  of  these 
three  grades  of  fineness,  are  shown  in  Fig  2,  which  is  similar  to  diagrams 
used  in  connection  with  alloys  of  three  metals. 


947  a 


CEMENT   MORTAR. 


14.  After  a  given  mixture  has  been  analyzed,  and  its  percentages  of  the 
three  grades  thus  determined,  it  is  plotted,  in  the  triangle,  by  a  point  so 
placed  that  its  perp  dists,  from  the  three  sides,  respectively,  of  the  equi- 
lateral triangle,  are  as  follows: 

distance  from  side  c     =  percentage  of  coarse     grains; 
"    m    =  "  medium 

"    /     =  "  fine 

15.  The  plotting  of  the  points,  and  the  measurements  of  their  dists,   are 
facilitated  by  the  lines  drawn  parallel  to  the  three  sides  respectively. 

16.  Thus,  point  a  represents  a  sand  having  20  %  fine  grains,  30  %  medium 
and  50  %  coarse,  as  shown  by  the  three  scales;  20,  30  and  50  being  the  dists 
of  a  from  sides  /,  m  and  c,  respectively. 

17.  When  a  series  of  experiments  has  been  made,  upon  any  given  quality 
(as  density  or  porosity,  etc,  etc)  of  sand  or  mortar,  as  affected  by  diffs  in 
mixtures  of  the  three  finenesses,  they  are  plotted  in  this  way,  and  "contour" 
or  "  iso  "-lines  are  drawn  thru  those  points  which  represent  equal  results 
in  the  quality  experimented  upon.     Each  "iso "-line  therefore  represents  a 
series  of  diff  mixtures,  each  of  which  will-  give  the  value  (as  to  density  or 
porosity,  etc,  etc)  represented  by  it. 

18.  Thus,  in  Fig  3  (T  &  T,  p  144,  Fig  51)  the  four  contours  and  the  point 
(0.610)  represent  five  diff  mixtures  of  coarse,  fine  and  medium  sands,  said 
mixtures  having  densities  (see  U  20)  of  0.525,  0.550,  0.575,  0.600,  0.610, 
respectively. 

I>ensity. 

19.  Specific  gravity  or  unit  weight.     Solid  quartz  weighs  about 
165  Ibs  per  cu  ft  =  2.643  grams  per  cu  cm;  sp  gr  =  2.64  to  2.67. 

20.  In  mechanics  (see  p.  338,  Art.  14  a)  density  is  defined  as  the 

mass  in  unit  volume.  In  sand,*  the  solid  portions  have  practically  constant 
sp  gr.  Hence,  for  a  given  sand,  "density"  is  used  to  designate  the  vol  of 
solid  in  unit  vol  of  sand,  or  the  ratio  of  solid  to  total  vol.  This  ratio  is 
sometimes  called  the  "absolute  volume."  Thus,  in  unit  vol  of  sand, 
"density"  =  1  —vol  of  voids. 

21.  The  greater  the  density  of  sand,*  the  less  cement  will  be  reqd  for  a 
given  quantity  of  mortar. 

22.  The  weight,  per  cubic   foot,  of    a    sand,*    of    given    sp    gr. 
varies  directly  with  its  density;  and  this,  in  turn,  depends  upon  the  shape 
of  the  grains,  upon  their  range  of  size,  upon  the  compacting  accomplished, 
as  by  shaking,  tamping,  etc,  and  upon  the  dryness  of  the  sand. 


^  Voids,  percentage  of  total  volume. 

8  g  8  5  8 

; 

i 

^ 

X 

1UU 

.  i 

• 

/* 

x"^ 

so1 

Vo 

*ds 

/ 

/ 

/^ 

Le. 

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fe 

</ 

W  g, 

1 

40  a, 

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/ 

X 

^ 

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li 

d 

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in 

dscal 

3 
20** 

x 

y 

X 

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0 

)       0.2      0,4      0. 
)            20 

0.8 
0           6 
Weigh 
Fig  4 

L.O      1-2       1.4       16       1.8      2.0      2.2       2.4      2.6  Qrams/cu.c 
)           80          100         120         140          mu*/<*'ft. 
t  per  unit  of  volume. 
Ratio  of  Solids  and  Voids. 

*  See  foot  note*,  p  946. 


SAND.  947  b 

23.  Fig  4  shows  the  relation  betw  (1)  the  unit  weight  and  (2)  the 
centages  of  solid  and  of  voids,  solid  quartz  weighing  as  in  H  19. 


percentages 


Effect  of  Moisture. 


24.  The  effect  of  moisture,  upon  the  vol  of  a  given  quantity  of 
sand,*  is  affected  by  the  vol  of  air  introduced,  by  the  quantity  of  water,  and 
by  the  shape  of  the  grains. 

See  HI]  29  to  31. 

25.  It  is  impracticable  to  measure  the  vol  of  air  introduced,  and  its 
presence  vitiates  all  observations.     When  sand  grains  are  dropped,  one  at  a 
time,  into  water,  most  of  the  air,  surrounding  the  grains,  is  left  behind  in 
the  atmosphere;  but  when  sand*  is  thrown  into  water  in  masses,  or  when 
moist  or  wet  sand  is  turned  over  by  shoveling,  considerable  and  unknmvn 
quantities  of  air  are  entrained  with  it. 

26.  In  moist  sand,*  the  total  (or  "absolute")  vol  of  voids  is  usually 
filled  partly  by  water  and  partly  by  air. 

27.  Within  a  certain  limit,  moisture  increases  the  adhesion  betw  the 
grains  of  sand,  and  thus  opposes  their  sliding,  one  upon  the  other,  conse- 
quently opposing  the  compacting  of  the  sand;  but,  beyond  that  limit,  it 
acts  as  a  lubricant  and  facilitates  the  compacting.     See  H*  24,  25. 

28.  Let 

V     —  volume,  in  cu  ft,  of  dry  quartz  in  1  cu  ft  of  sand;* 

v      =  "voids  "  1    '  "    ;   V  +  v   =   1  cu  ft; 

W    =  wt,  in  Ibs,  of  1  cu  ft  of  pure  solid  quartz  =  165; 

w     =     '  "  1  "        "    the  sand  (dry  or  moist,  as  the  case  may  be); 

d      =     '  "  dry  quartz  in  1  cu  ft  of  the  sand;   (in  dry  sand,  d  =  w). 

P     =     '  "  water  added  to  1  Ib  of  dry  sand;* 

in  (1  +  P)  Ibs  of  moist  sand; 
p     =    ......     '  .....  1  Ib       "       "         "  ; 

m     =     '  1  cu  ft  "  "   .' 

Then  p/P  =  !/(!+  P);       and  p  =  P/(l  +  P); 

m  =  w  p',       d  =  w  —  w  p  =  w  (I  —  p); 

V  =  (w  —  w  p}/W  =  rf/165;       v  =  1  —  V  =  1  —  rf/165; 


1  —  p  I  —  p' 

29.  The  proportion,  p,  of  moisture  (Ibs  of  water  in  1  Ib  of  moist 
sand),  is  ascertained  by  heating  a  known  wt  of  the  moist  sand,  at  not  less 
than  100°  C  (212°  F),  until  no  further  loss  of  wt  takes  place,  and  noting  the 
loss  of  wt.  Then: 

loss  of  weight  -:   original  weight  of  portion  heated, 
dry  sand  (Fig  4)  p  =  0,       w  p  =  0,       w  =  d  ;  and  we  have: 
V  =  w/\V  =  MJ/165  =  d/165. 


p 
In 


Effects  of  Shape  and  Size. 

30.  Spherical  grains.     If  a  number  of  spheres,  of  uniform  diam, 
D,  be  piled  as  closely  as  possible,  the  ratio  of  vol  of  solid  to  total  vol  is 

„       =  about  0.74;  and  the  voids  (about  0.26  X  the  total  vol)  are  of  two 

o 

sizes,  such  that  they  can  be  fitted,  respectively,  with  spheres  having  diams 
=  about  0.41  D  and  0.22  D.     (T  &  T,  pp  169-170.) 

31.  Effect  of  gradation  of  sizes.     The  proportion  of  voids   may 
be  indefinitely  reduced  by  adding  to,  and  mixing  with,  the  original  grains, 
smaller  and  smaller,  or  larger  and  larger,  particles,  in  proper  proportions, 
each  size  occupying  a  portion  of  the  voids  left  between  the  particles  of  the 
size  next  coarser.     With  spherical  particles,  therefore,  the  voids  are  greatest, 
and  the  wt  per  unit  vol  least,  when  the  grains  are  of  uniform  size.     This 
seems  to  hold  true  also  for  particles  of  other  shapes. 

*  See  foot-note*,  p  946. 
C4 


947  C  CEMENT   MORTAR. 

Other  Properties. 

32.  Turbidity  test  for  silt  in  sand.  Separate  the  silt  from  a 
considerable  quantity  of  sand,  and  make  up  a  special  sample  containing  the 
max  proportion  of  silt  allowed  by  the  spec'n.  Place  a  small  known  portion 
of  this  mixture  in  a  known  quantity  of  clear  water  in  a  graduated  vessel. 
Shake  the  vessel  until  the  sample  is  thoroly  washed.  Insert  a  pin  horizon- 
tally in  the  side  of  a  stick  near  its  end,  insert  that  end  of  the  stick  into  the 
vessel,  lowering  it  until  the  pin  is  no  longer  visible  thru  the  liquid,  and  note 
the  depth  of  the  pin  by  means  of  the  graduation.  Make  several  such  tests 
and  note  the  average  depth  of  disappearance  of  pin.  In  testing  samples, 
if  the  pin  disappears  at  a  higher  elevation  than  the  standard,  the  sand  has 
more  silt  than  the  maximum  allowable,  and  vice  versa.  (W.  J.  Douglas, 
EN,  '06/Dec/20,  p  648.) 

:>:$.  Tbe  presence  of  clay  and  loam,  in  sand,  may  be  de- 
tected by  nibbing  the  damp  sand  in  the  hand,  and  observing  the  condition 
of  the  hand,  or  by  mixing  the  sand  with  clean  water  and  noting  the  effect 
upon  the  water. 

34.  Washing.     Dirty  sand  may  be  washed  in  a  specially  constructed 
sand  washer;  or,  by  means  of  a  jet  from  a  hose,  in  a  box  so  arranged  that 
the  mud,  clay  and  organic  impurities  are    floated  off,  leaving  the  heavier 
sand  behind. 

35.  Washing  may  carry  off  the  finer  particles  of  a  well  assorted  sand, 
leaving  it  less  dense  than  before.     It  is  well  to  test  a  small  quantity  of  the 
eand,  washed  and    unwashed,  before  arranging  to  wash    for  use.     (Jas.  C. 
Hain,  E  R,  '05/Jan/28,  p  105.) 

36.  The  degree  of  sharpness  of  a  sand  may  be  estimated  by 
means  of  the  sound  emitted  by  it  when  kneaded  betw  the  hands   or  more 
cloeely  estimated  by  means  of  a  magnifying  glass. 


MORTAR.  947  d 

MORTAR.* 

Constituents. 

1.  Cement  mortar  consists  of  cem,  mixt  with  water,  with  or  without 
some  inert  granular  material,  as  sand,  fine  grayel,  stone  or  gravel  screenings, 
or  ground  cinder.     Without  sand,  etc.,  the  mixture  is  called  neat  mortar, 
or  cement  paste. 

Amount  of  Mortar  Required  for  a  Cubic  Yard  of  Masonry.f 

Mortar. 
Description  of  Masonry.  Cu  yd. 

Min.    Max. 

Ashlar,  18"  courses  and  YS  joints 0.03      0.04 

"       12"        "         "       "       "      0.06      0.08 

Brickwork  (bricks  of  standard  size,  8 MX  4  X  2M  ins.): 

y%"  joints 0.10      0.15 

Ys"  to  W  joints 0.25      0.35 

%"  to  H"  joints 0.35      0.40 

Rubble,  of  small,  rough  stones 0.33      0.40 

"  large  stones,  rough  hammer-dressed 0.20      0.30 

Squared-stone  masonry,  18"  courses  and  M"  joints 0.12      0.15 

"        12"        "  "       "       "      0.20      0.25 

2.  Effect    of   roasting    and    of  subsequent   wetting-.     The 
materials,  of  which  cem  is  made,  are  inert  or  stable  compounds,  remaining 
practically  unchanged  under  ordinary  conditions;  but  when,  in  burning, 
the  calcareous  materials  are  subjected  to  high  temps,  either  alone  or  mixed 
with    argillaceous    materials,    relatively    unstable    compounds    are    formed, 
ready  to  enter  into  new  and  again  stable  compounds  when  their  particler 
are  brought  into  intimate  contact  by  being  mixed  with  water,  the  water  also 
entering  into  the  new  combinations.     The  mixture  then  soon  "sets"  (loses 
plasticity),  and,  shortly  thereafter,  begins  to  solidify  and  harden. 

See  H '8,  Cement,  p  931. 

3.  In  the  process  of  crystallization,  the  alumina  appears  to  act  chiefly  as 
a  flux,  promoting  the  formation  of  the  lime  silicate,  upon  which  the  success 
of  the  operation  depends.     Iron  oxide,  which  is  generally  present,  seems  to 
answer  as  well  as  alumina,  as  a  flux,  and  it  requires  a  less  high  temp  for 
calcination. 

4.  The  proportion  of  sand,  which  should  be  used  in  any  given  case, 
cannot  be  properly  stated  without  stating  also  its  range  of    size,  or  the 
proportion  of  voids  to  the  whole  mass;  but,  in  general,  good  Portland  cems 
will  "carry"  from  2  to  3  vols  of  sand;  nat  cems  from  1.5  to  2  vols. 

5.  Approximate  quantities  of  Portland  cement  and  loose 
sand  per  en  yd  of  mortar. 

Neat       1:1        1:2        1:3        1:4        1:5        1:6 

bbls  cem 8.0       4.6        3.1        2.3        1.8        1.5        1.3 

cu  yds  loose  sand 0  0.65      0.87      0.97      1.02      1.06      1.10 

Cement  in  Mortar. 

See  also  CEMENT,  p  930. 

6.  Owing  to  the  cheapness  with  which  cements  are  now  manufactured, 
and  the  superiority  of  the  mortars  made  from  them,  the  latter  have  to  a 
great  extent  superseded  lime  mortars,  even  in  ordinary  building 
operations. 

7.  In  selecting  cem,  a  reputation,  gained  by  years  of  successful  use 
and  experiment,  is  of  greater  value  than  the  results  of  a  few  tests;  but  such 
tests  are  of  value  for  excluding  inferior  parcels  of  such  accepted  brands. 

8.  High  grade  cements  are  usually  economical,  even  at  a 
higher  cost,  as  they  allow  the  use  of  a  larger  proportion  of  the  cheaper  in- 
gredients, sand,  gravel  and  broken  stone. 

*As  the  strgth,  permeability,  etc,  of  a  cone  depend  largely  upon  those  of 
its  mortar,  we  discuss,  under  "mortar,"  many  of  its  properties  commonly 
discussed  under  "concrete" 

t Taken,  by  permission,  from  "A  Treatise  on  Masonry  Construction,"  by 
Prof.  Ira  O.  Baker.  New  York,  John  Wiley  &  Sons.  9th  edition,  1907. 


947  e  CEMENT   MORTAR. 

9.  Free  Lime.     Cem  may  contain   "free"    (uncombined)  lime   as   a 
result  (1)  of  insufficient  manipulation  of  the  raw  materials,  (2)  of  insufficient 
burning,  (3)  of  an  excess  of  lime  carbonate  (CaCO3)  in  the  raw  materials,  or 
(4)  of  adulteration  after  burning  and  grinding. 

10.  This  lime  may  be  present  either  as  quick  lime,  CaO,  or  as  slacked 
lime  Ca(OH)2,  either  of  which  may  be  washed  out  (the  CaO  first  becoming 
Ca(OH)2)  by  infiltrating  water.     This,  of  course,  weakens  the  cem. 

11.  Slacked  lime  takes  no  part  in  the  hardening  process,  but  remains 
as  an  inert  filling  material. 

12.  Quick    lime  slacks  by  absorption  of  the  water  used  in  mixing; 
and,  when  the  burning  has  been  at  a  high  temp,  the  slacking  is  delayed.     If 
it  takes  place  during  the  setting  of  the  cem,  the  swelling  of  the  lime  weakens 
the  cem  by  rendering  it  porous.     If  slacking  is  delayed  until  after  harden- 
ing, and  if  the  expansive  force  is  sufficient,  the  cem  is  disintegrated. 

13.  Excess  of  lime  retards  setting,  and  reduces  soundness. 

14.  Free  Magnesia.     Much  uncertainty  exists  as  to  the  effect  of  free 
magnesia,  in  diff  proportions,  in  cem.     Like  lime,  it  expands  when  wet,  but 
much  more  slowly;  and  its  presence  may  therefore  remain  unsuspected  until 
too  late.     I>olomite,   or  magnesian  limestone,  contains  about  45  %  of 
magnesia.     Formerly,  1.5  %  of  free  magnesia,  in  cem,  was  considered  dan- 
gerous.    It  is  now  generally  believed  that  more  than  from  3  to  5  %  weakens 
the  cem,  and  that  8  %  or  more  causes  cracking.     In  any  proportion,  it  is 
probably  objectionable,  at  least  as  displacing  an  equal  quantity  of  the  more 
valuable  lime. 

Sand*  in  Mortar. 

See  also  SAND,  pp  946,  &c. 

15.  The  quality  of  the  concrete  depends  upon  the  strength  of  the  mortar, 
and  this,  in  turn,  depends  largely  upon  the  character  of  the  sand.  . 

16.  For  a  given  proportion  by  wt,  the  best  sand  is  that  which  produces  the 
smallest  vol  of  plastic  mortar. 

17.  Weight.     As  betw  two  sands,  of  a  given  material,  the  heavier  of 
course  has  the  smaller  vol  of  voids. 

18.  Fineness.     A  fine  sand,  well  assorted  as  to  sizes  of  grain,  and 
therefore  dense,  may  make  better  mortar  than  a  coarser  sand,  with  grains 
of  more  nearly  uniform  size  and  therefore  less  dense. 

19.  Extreme  fineness  prevents  penetration  of  the  paste  betw  the 
grains,  and  delays  setting. 

20.  Mortars  made  with  fine  sand,  altho  less  permeable  than  those  made 
with  coarse  sand,  are  apt  to  be  more  easily  acted  upon  by  sea  water. 

21.  Shrinkage.     Mortars,  with  coarse  sand,   shrink  less  than  those 
with  fine  sand. 

22.  Sharpness.     It  has   been  customary  to  insist  upon  sharpness  of 
grain,  in  sand  used  for  mortar,  probably  owing  to  the  impression  that  sharp 
grains  form  a  better  bond  with  the  cem  or  that  sharpness  indicates  freedom 
From   impurities;  but    the    advantage    is    doubtful.     Sands    with    rounded 
grains  are  commonly  used,  and  with  entirely  satisfactory  results;  and  the 
laboratory  tests  generally  indicate  that  sharp-grained  sands  have  no  marked 
superiority      Roundness  of  grain  facilitates  the  packing,  and  thus  increases 
the  density  of  the  sand. 

23.  The  Board  of  Public  Works  of  Porto  Rico,  with  briquettes  of  1  :  2 
mortar,  found  25  %  greater  strgth  with  washed  than  with  unwashed 
sand.     Sand,  containing  much  foreign  matter,  should  be  tested  before  being 
accepted. 

24.  In  general,  the  evidence,  as  to  the  relative   values  of  sand 
and  of  screenings,  appears  to  be  favorable  to  the  use  of  screenings  (see 
Experiments),  but  opinion  is  divided.     The  hydraulicity  of  the  dust, 
in  the  screenings,  may  add  to  the  strength  of  the  mortar. 

25.  Harry  Taylor,  Capt,  Corps  of  Engrs,  USA,  tested  1650  briquettes- 
of  1-  :  3,    1:4  and  1  :  5  mortars,  at  1,  3,  6  and  12  mos,  with  standard  crushed 
quartz,  Plum  Island  sand  and  crusher  dust.     Crusher  dust  gave  briquets 

*  See  foot-note,  SAND,  U  1,  p  946 


MORTAR.  '  947/ 

2.3  times  stronger  than  sand,  and  72  %  stronger  than  quartz.  1  :  5,  with 
stone  dust,  stronger  than  1  :  3  quartz. 

20.  G.  J.  Griesenauer,  E  N,  '03/Apr/16,  p  342.  Chicago,  Mil  &  St  P  RR, 
225  tests,  as  follows  : 

Limestone  screenings,  1  :  3,  passing  No  12,  held  on  No  40  sieve, 
averaged  74  %  better  than  Hammond  pit  sand,  1:3;  with  all  sizes  used, 
they  averaged  115  %  better.  Mortar  of  1  :  6  screenings  was  23  %  stronger 
than  1  :  3  sand,  dtravel  screening's  were  not  much  better  than  sand. 

27.  Maryland  highways.     Briquettes,  made  with  stone  screening's, 
were  34  to  62  %  stronger  than  with  Potomac  River  sand. 

Lime  in  Mortar. 

28.  The  substitution  of  10  %  to  20  %  lime  paste  for  an  equal 
vol  of  cem  paste,  reduces  the  cost  of  the  mortar,  renders  it  less  "short", 
and  slightly  retards  setting,  without  seriously  diminishing  its  strgth.     Larger 
quantities  reduce  strgth.     (Baker,  Masonry  Construction.) 

29.  Feret  found  the  effect  of  lime  dependent  upon  the  richness  of  the  cem 
mortar.     With  1  :  4  cem  mortar,  the  addition  of  4  to  5  %  of  dry  slaked  lime 
increased  the  strgth;  while,  with  1  :  1.25  cem  mortar,  the  addition  of  lime 
lowered  the  strgth.     (Chimie  Appliquee,  1897,  p  481.) 

Clay  in  Mortar. 

30.  Laboratory  tests  indicate  that   a  small    admixture  of  clay 

increases  rather  than  diminishes  the  strgths  of  mortar,  and  diminishes  its 
permeability;  but,  in  actual  work,  the  clay  particles  tend  to  adhere  and 
thus  to  form  lumps  having  but  slight  cohesion. 

31.  Laboratory  conditions,  as  to  dryness,  pulverization,  etc.,  cannot  be 
reproduced  in  practice. 


32.  When  the  clay  occurs  naturally  in  the  sand,  it  may  not  be  practicable 
to  effect  a  perfect  mixture  and  distribution. 

33.  Clay,  etc,  are  more  likely  to  give  trouble  with  dry  than  with  wet 
mixtures. 

Consistency. 

34.  Relative  strengths  of  dry  and  wet  mortars,  1:  1.     Alfred 
Noble,  over  5000  experiments.     Strength  of  dry  mortar  taken  as  100. 

T» xl 1 XT_A 1 


Age         30  days     3  mos    6  mos     1  yr       30  days     3  mos     6  mos    1  yr 
Dry  Mortar.  ...     100         100         100       100  100  100        100       100 

Moderately  stiff.     97  94  97         97  78  89          95         90 

Grout 90  92  91         95  63  77          86         82 

35.  Use  dry  cone  when  it  is  to  be  heavily  loaded  at  once.     Tests  indicate 
that  wet  and  dry  cone  will  be  equal  in  strgth  within  a  year. 

36.  Wet  cone  bonds  better  to  9ld  work  than  does  dry  cone.     Excess  of 
water  increases  efflorescence  and  laitance. 

37.  Rule   for    percentage,   W,   of  water.     H.  P.  Gillette,  Cost 
Data,  p  266. 

Let  S  =  parts  of  sand  to  1  part  cem.     Then 

W  =  (8S  +  24)  -H  OS  +  1). 
This  gives 

when  S  =     1  1.5  2.Q  2.5  3.0  3.5  4.0 

W  =   16  14.4          13.3          12.6         12.0  11.5          11.2 

Falk  finds  that  mortars,  thus  proportioned,  adhere  well  to  steel. 

38.  Slag  cement  requires  plenty  of  water  for  its  proper  hardening. 
•  Therefore,  if  used  in  air,  slag  cem  mortar  should  be  kept  damp. 

Setting  and  Hardening. 

39.  Setting,  or  the  loss  of  plasticity,  usually  occurs  within  a  few  hours 
(sometimes  within  a  few  minutes)  after  mixing  cem  with  water;  whereas 
hardening  and  increase  of  strength  (which  appear  to  result  from  a 
different  set  of  chemical  processes)  often  proceed  for  months  or  even  years, 

63 


CEMENT   MORTAR. 

40.  Molded  blocks  of  Portland  cone,  of  even   50  tons  wt,  can 
generally  be  handled  and  removed  to  their  places  in  from  1  to  2  weeks 

Initial  and  Final  Set. 

41.  Initial  and  final   set   are  stages  of  the  setting  process,  arbi- 
trarily distinguished  by  means  of  the  resistance,  of  the  mortar,  to  penetra- 
tion by  cylindrical  wires,  of  standard  dianis  and  loaded  with  standard  wts, 
the  blunt  ends  of  the  wires  resting  upon  the  surf  of  a  pat  of  the  mortar, 
formed  in  a  flat  cylindrical  mold  on  a  glass  plate.     See  ^  8,  p  943. 

Determination  of  Set. 

42.  Genl  Tottcii,   (Genl  Q.  A.  Gillmore,  Limes,  Hydraulic  Cements  and 
Mortars,  p  80,)  at   Fort  Adams,  R.  I.,  prior  to  1830,  used  a  Ha  inch  wire, 
loaded  with  0.25  Ib,  and  a  J/k  inch  wire,  loaded  with  1  Ib;  initial  and  final 
set  being  taken  as  the  conditions  when  these  wires,  respectively,  failed  to 
make  an  impression  upon  the  mortar. 

43.  Vicat  used  but  one  wire,  or  "needle."     The  A  S  C  E  (see  specifica- 
tions, p  943)  prescribes,  for  this  needle,  a  diam  of  1  mm  (0.039  inch)  and  a 
load  of  300  grams  (10.58  oz).     Initial  set  occurs  when  the  end  of  the  needle, 
penetrating  a  pat  of  mortar  4  cm  (1.57  ins)  deep,  can  no  longer  approach 
within  5  mm  (0.2  in)  of  the  glass  plate;  and  final  set  when  the  needle  fails 
to  sink  visibly  into  the  mortar.     The  mortar,  under  the  setting  test,  must 
be  of  "normal  consistency,"  or  such    that  a  cylindrical    rod,  1    cm 
(0.39  inch)  in  diam,  loaded  with  300  grams,  its  end  resting  upon  the  mortar, 
penetrates  1  cm  into  it. 

Speed. 

44.  Speed.     Some  of  the  best  cems  are  the  slowest  setting.     A  layer  of 
very  quick-setting  cem  may  partially  set,  especially  in  warm  weather,  before 
the  masonry  is  properly  lowered  and  adjusted  upon  it,  and  any  disturb- 
ance, after    setting  has    commenced,    is    prejudicial.     On   the  other 
hand,  quick-setting  cements  are  best  in  certain  cases,  as  when  exposed 
to  running  water,  etc.     They  may  be  rendered  slower  by  adding  a  bulk  of 
lime  paste  equal  to  5  or  15  %  of  the  cement  paste,  without  weakening  them 
seriously.     Nat  cems  usually  set  quickly.     Slag  cem  sets  slowly. 

45.  In  general,   setting  is  accelerated   by  high   alumina  and   by 
soda  and  potash  in  the  cem,  by  freshness  and  fineness  of  the  cem,  by  the  use 
of  warm  water  and  warm  sand   in   mixing,  and    by  warm  weather.     Set- 
ting* is  retarded  by  excess  of  lime  and  silica  in  the  cem,  by  the  presence 
of  sand,  by  wetness  of  mixture,  by  cold,  by  retempering,  by  salt  or  sulfuric 
acid  in  the  mixing  water,  by  the  presence  of  1  or  2  %  of  lime  sulfate,  either 
hydrated  (gypsum)  or  anhydrous  (plaster  of  Paris)  or  of  slaked  lime,  in  some 
cases  by  hard  burning,  and.  in  general,  by  the  age  of  the  cement,  but  the 
storage  of  new  cem  in  warm  places  accelerates  setting. 

45  a.  Gypsum.  CaSO4.  Time  of  setting  (initial  and  final)  increased 
rapidly  with  additions  of  gypsum  up  to  about  2  %,  and  remained  constant, 
or  increased  slightly,  up  to  4  %.  E.  Candlot,  "Ciments  et  Chaux  Hydrau- 
liques." 

45  b.  Time  of  setting  (initial  and  final)  increased,  up  to  about  1.5% 
gypsum,  but  then  decreased,  as  the  gypsum  was  increased  to  7  %.  Knis- 
kern  and  Gass,  Sibley  Jour  of  Engng,  '05,  Jan. 

45  c.  Calcium  chloride,  CaCl2.  A  weak  solution  retards,  but  a 
concentrated  solution  accelerates,  the  setting  of  Port  cems.  Thus,  with  10 
to  40  grammes  per  liter,  the  time  of  setting  reached  500  to  850  mins  ;  while, 
with  200  to  300  grammes  per  liter,  it  was  reduced  to  from  2  to  25  mins. 
Cems  with  very  high  or  very  low  alumina  are  but  little  affected  by  CaCl2. 
A  weak  solution  (30  to  60  grammes  per  liter)  may  render  sound  a  cem  con- 
taining free  lime,  by  facilitating  the  hydration  of  the  lime.  E.  Candlot, 
"Ciments  et  Chaux  Hydrauliques. " 

45  d.  From  %  to  \%  %  dry  CaCl2,  ground  with  cem  clinker  and  made 
into  pats  of  normal  consistency  (See  Tests,  H  7,  p  943)  increased  the 
time  of  initial  set  from  2  to  167  mins,  and  that  of  final  set  from  52  to  275 
mins.  With  6  %,  the  times  were  68  and  145  mins  respectively,  Kniskern 
and  Gass,  Sibley  Jour  of  Engng,  '05,  Jan. 

46.  Setting  is  attended  by  an  increase  of  temperature.     In  quick 
setting,  this  increase  may  amount  to  10°  C  (18°  V)  or  more. 


MORTAR.  947  /i 

47.  Slow  setting  cems  are  apt  to  harden  more   rapidly   than  quick 
setting. 

48.  In  warm  air,  setting  cem,   in  drying,  loses  the  moisture  upon 
which  the  operation  of  hardening  depends.     It  therefore  sets  without 
hardening-.     In  hot  weather  every  precaution  should  be  taken  against 
this. 

49.  Cems  of  the  same  class  differ  much  in  their  rapidity  of  harden- 
ing-.    At  the  end  of  a  month  one  may  gain  nearly  one-half  of  what  it  will 
gain  in  a  year,  and  another  not  more  than  one-sixth;  yet  at  the  end  of  a 
year  bolh  may  have  about  the  same  strength.     Hence,  tests  for  1  week 
or  1  month  are  by  no  means  conclusive  as  to  the  final  comparative  merits 
of  cements. 

50.  Many    years    are    required     to     attain     the    greatest 
hardness:    but  after  about  a  year  the  increase  is  usually  very  small  and 
slow,  especially  with  neat  cem.  Moreover,  any  subsequent  increase  is  a  matter 
of  little  importance,  because  generally  by  that  time,  and  often  much  sooner, 
the  work  is  completed  and  exposed  to  its  max  loads. 

51.  Cems  which  are  slow-setting  when  made,  are  apt  to  become  quick- 
setting   (or   "flashing"*)  when  stored,  especially  in  warm  places, 
and  if  the  cem  is  underlimed.      This  is  attributed  to  disintegration  of  the 
particles  and  consequent  increase  in  fineness.     The  change  sometimes  take* 
place   very   quickly.     This   difficulty   can    usually   be    overcome,    without 
reducing  the  strgth,  by  storage  in  cool   places  and  by  adding   1  to  2%  of 
slaked  lime.     Oh  small  jobs,  a  few  lumps  of  lime  may  be    added  to  each 
bbl  of  mixing  water. 

52.  The  requirement,  not  uncommon  in  specfns,  that  a  certain  percent- 
age of  increase  of  strength  must  take  place  between  7  and  28 
days,  tempts  the  mfr  to  grind  the  cem  coarsely,  or  to  adulterate  it  with 
inert  material,  in  order  that  it  may  not  gain  too  much  of  its  strgth  within 
the  first  7  days. 

Properties. 
Soundness. 

53.  ITnsoundness,  in  cem  mortar,  is  the  tendency  to  expand,  contract 
or  disintegrate  in  air  or  water,  or  under  heat  and  cold.     See  Specifications. 

54.  Cem,  of  any  established  brand,  will  seldom  be  found  deficient  in 
strength;  but  may  be  deficient  in  soundness,  upon  which  durability  depends. 

55.  Unsoundness    is    generally  due  to  excess  of, free  lime,  arising 
from  incorrect  proportioning,  overburning,  lack  of  seasoning,  or  coarseness 
of  grinding;     the   latter  preventing  perfect   hydration.     The    presence  of 
lime  sulphate  (gypsum    plaster  of  Paris)   is   favorable   to  soundness. 
Unsound  cern  is  improved  by  storage. 

56.  Change  of  dimensions  during  hardening  of  concrete. 
Cone,  placed  in  air,  shortens  or  shrinks  during  the  first  two  or  three 
months;  while  cone,  in  water,  expands  during  about  the  same  time. 
These  changes  are  greater  with  those  cones  having  the  larger  proportions 
of  cem. 

57.  Shrinkage  of  mortar  set  in  air. 

per  cent.  ins.  per  100  ft. 

Neat  cement,* 0.132  to  0.140  1.58  to  1.68 

Mortar,  1  :  1,* 0.080  to  0.170  0.96  to  2.04 

Lean  mortars.t 0.030  to  0.050  0.36  to  0.60 

The  expansion  ill  water  is  somewhat  less  than  the  contraction  in  air. 
•  The  total  change  in  dimensions  is  the  algebraic  sum  of  that  due  to  setting, 
and  that  due  to  temperature  changes. 

58.  Cone  shrinks  less  when  it  sets  under  pressure.    Fineness  ot 
sand  is  conducive  to  shrinkage. 

*  Trans.  A  S  C  E,  Vol  xvii,  1887,  p  214. 

t  Considere.     Experimental  Researches  on  Reinforced  Concrete.     Trans- 
lation by  Moissieff ,  p  87. 


947  i 


CEMENT   MORTAR. 


Strength. 

59.  Cem  mortars  are  usually  tested  (by  means  of  briquets)  for  tensile 
strength. 

60.  Factors    affecting    strength.       The    strengths    of    samples, 
under  test,  are  much  affected  by  the  temperature  of  the  air  and  water,  as  also 
by  the  force  with  which  the  cem  is  pressed  into  the  molds;    by  the  extent 
of  setting  before  being  put  into  the  water,  and  of  drying  when  taken  out; 
and  still  more  by  the  pres  under  which  it  sets,  which  increases  the  strength 
materially.     On  this  account,  cems,  in  actual  masonry,  may,  under  ordi- 
nary  circumstances,    give   better   results   than   in   tests   of   samples.     The 
causes  named,  together  with  the  degree  of  thoroness  of   the  mixing,  the 
proportion  of  water  used,  and  other  considerations,  may  easily  affect  the 
results  100  %  or  even  much  more.     Hence  the  discrepancies  in  the  reports 
of   different   experimenters.      Specimens    of    the  same    cem,  tested  under 
apparently  similar  conditions,  may  give  widely  diff  results. 

61.  Personal  equation.      In  connection  with  the  building  of   the 
Croton  Aqueduct,  New  York,  one  set  of  testers,  testing  835  briquets,  ob- 
tained an  av  strgth  of   62.3  Ibs  per  sq    in;    while  another  set  of    testers, 
testing  2434  exactly  similar  briquets  by  the  same  methods  and  under  the 
same  circumstances,  obtained  an  av  strgth  of  85.2  Ibs  per  sq  in,  or  36  % 
greater. 

62.  Owing  to  such  uncertainties,  a  series  of  tests,  to  be  of  value,  must 
cover  a  large  number  of  specimens,  in  order  that  the  accidental 
diffs  may  be  averaged. 

63.  Diffs  in  comparative  results  with  diff  materials  may  be  due  to  one 
or  other  of  several  diffs  betw  the  materials.     Thus,  in  comparing  mortars 
made  with  clean  and  with  dirty  sands,  the  strgths  may  be  more  affected 
by  diffs  in  density  than  by  the  diffs  in  cleanness  of  the  sand. 

64.  Effect    of  age.     The    diagram,*    Fig  1,    illustrates     approx    the 
strengths  of  av  Portland  and  of  av  nat  cems,  neat  and  with  2  and  3  parts 


000 


14334        O 
Weeks       JUotithii 

Fig  1.     Age  and  Strength  of  Mortar. 


1 
Year 


2 
years 


of   sand,  up  to  an  age  of    two  years.     Tests  may  readily  vary  10  per  cent 
or  more  eitherway  from  the  average. 

*  See  Richard  L.  Humphrey,  in  "Cement,"  Chicago,  May,  1899. 


MORTAR. 


947J 


65.  Fig    2  *    shows,    approximately,   the    effect    of  sand, 

in  diti  proportions,  upon  the  strengths  of  Portland  and  natural  cements,  at  diff 


.S  700 


01        234567 

Parts  of  Sand  to  1  fart  Cement 

Effect  of  Sand  upon  Strength. 


Fig  2 


ages  from  1  week  to  1  year.  The  four  solid  curves  represent  average  Port- 
land cements,  and  the  four  dotted  curves  represent  average  natural  cements. 
For  each  kind  of  cement,  the  curves  represent  ages  of  1  year,  6  months,  1 
month  and  1  week,  respectively,  beginning  at  the  top.  The  curves  for 
natural  cement  are  carried  only  to  5  parts  sand. 

66.  The  compressive  strengths  of  cem  mortars,  in  cubes,  appear 
to  be  about  8  to  10  times  their  tensile  strengths,  and  their  shearing  strgths 
about  Vi  their  tensile  strgths. 

67.  The  adhesion  of   cem    mortars   to    bricks    or    rough 
rubble,  at  diff  ages,  and  whether  neat  or  with  sand,  may  be  taken  at  an 
av  of  about  %  the  tensile  strength  of  the  mortar  at  the  same  age.     If  the 
bricks  and  stone  are  moist  and  entirely  free  from  dust  when  laid,  the  ad- 
hesion is  increased;  whereas,  if  very  dry  and  dusty,  especially  in  hot  weather, 
it  may  be  reduced  almost  to  nothing.     The  adhesion  to  very  hard,  smooth 
bricks,  or  to  finely  dressed  or  sawed  masonry,  is  less  than  the  adhesion  to 
rough  and  porous  surfs. 

68.  Dr.   Bohme,  Berlin,  found    tensile   strgth  -=-  adhesive   strgth  =  10, 
with  1  :  3  and  1  :  4  mortars,  and  =  6  to  8,  with  neat  and  1  :  2  mortars. 

Finish. 

69.  Lime  mortar  and  cems,  when  used  as  mortar  for  brickwork,  often 
disfigure  it,   especially   near  sea-coasts,   and  in  damp   climates    by  white 
efflorescence,  which  sometimes  spreads  over  the  entire  exposed  face  of 
the  work,  and  also  injures  the  bricks.     This  occurs  also,  to  some  extent, 
with  Portland  cems;    also  in  the  mortar  joints  of  stone  masonry,  but  to  a 
much  leas  extent.     It  injures  only  porous  stone.     It  is  usually  a  hydrous 
soda   or   potash   carbonate,   or   magnesia    sulfate   (Epsom  salts)    often  with 
other    salts.      As    a    preventive,    General    Gillmore  recommends    to  add  to 
every  300  Ibs  (1  bbl)  of  the  cem  powder,  100  Ibs  of  quicklime,  and  from 
8  to  12  Ibs  of  any  cheap  animal  fat;    the  fat  to  be  well  incorporated  with 
the  quick- lime  before  slacking  it,  preparatory  to  adding  it  to  the  cem. 
This  addition  will  retard  the  setting,  and  somewhat  diminish  the  strength 
of  the  cem.     It  is  said  that  linseed  oil,  at  the  rate  of  2  gals  to  300  Ibs  of  dry 
cem,  either  with  or  without  lime,  will,  in  all  exposures,  prevent  efflorescence; 
but,  like  the  fat,  it  greatly  retards  setting,  and  weakens  the  cem.     See  also 
Bricks,  p  929. 

70.  For  pointing,  the  best  Portland  cem  should  be  used,  and  is  best 
used  neat,  but  it  is  often  used  with  from  1  to  2  parts  of  sand.     Mix  under 
shelter,  and  in  quantities  of  only  2  or  3  pints  at  a  time,  using  very  little 
water;   so  that  the  mortar,  when  ready  for  use,  shall  appear  rather  incoherent, 
and  quite  deficient  in  plasticity.     The  joints  being  previously  scraped  out 

*  Compiled,  by  permission,  from  Prof.  Baker's  "Masonry  Construction." 


947  k  CEMENT   MORTAR. 

to  a  depth  of  at  least  half  an  inch,  the  mortar  is  put  in  by  trowel;  a  straight- 
edge being  held  just  below  the  joint,  if  straight,  as  an  auxiliary.  The 
mortar  is  then  to  be  well  calked  into  the  joint  by  a  calking-iron  and  hammer; 
then  more  mortar  is  put  in  and  calked,  until  the  joint  is  full.  It  is  then 
rubbed  and  polished  under  as  great  pressure  as  the  mason  can  exert.  If 
the  joints  are  very  fine,  they  should  be  enlarged  by  a  stonecutter,  to  about 
^4  inch,  to  receive  the  pointing.  The  wall  should  be  well  wet  before  the 
pointing  is  put  in,  and  kept  in  such  condition  as  neither  to  give  water  to, 
nor  take  it  from,  the  mortar.  In  hot  weather  the  pointing  should  be  kept 
sheltered  for  some  days  from  the  sun,  so  as  not  to  dry  too  quickly. 

Behavior  in  Water. 

71.  Ijaitance.     "When  cone  is  deposited  in  water,  especially  in  the  sea, 
a  pulpy  gelatinous  fluid  exudes  from  the  cem,  and  rises  to  the  surface.     This 
causes  the  water  to  assume  a  milky  hue;   hence  the  French  term,  laitance. 
As  it  sets  very  imperfectly,  and,  with  some  varieties  of  cems,  scarcely  at  all, 
its  interposition  betw  the  layers  of  cone,  even  in  moderate  quantities,  will 
have  a  tendency  to  lessen,  more  or  less  sensibly,  the  continuity  and  strgth 
of  the  mass.     It  is  usually  removed  from  the  inclosed  space  by  pumps, 
which  must  be  used  cautiously,  to  avoid  disturbance  of  the  cone  by  currents. 
The  proportion  of  laitance  is  greatly  diminished  by  reducing  the  area  of 
cone  exposed  to  the  water,  as  by  using  laroe  boxes,  say  from  1  to  1.5  cu 
yds  capacity,  for  immersing  the  cone."     (Gillmore,  "Limes,  Hyd.  Cems  & 
Mortars.") 

72.  Authorities  differ  as  to  the  effect  of  sea  water.     H.  LeChatelier 
(Internatl  Assn  for  Testg  Materials,  Procs,  1906),  finds  that  the  active  in- 
gredients of  cem  (lime,  aluminates,  silicates)  are  decomposed  by  the  magne- 
sium salts  of  sea  water,  yielding  soluble  calcium  chlorides  and  lime  sulfates. 
The  latter,  with  lime  aluminate,  forms  a  compound  whose  crystallization 
tends  to  swell  and  crack  the  material. 

73.  In    view  of    the  notable  puddling  effect  of   percolating  water, 
it  would  appear  that  sea  water  especially,  with  its  numerous  salts,  ought 
shortly  to  block  its  own  passage  into  the  cone. 

74.  The  substitution  of  iron  for  alumina,  in  cem,  is  found  to 
remove  one  of  the  most  active  reagents  in  the  deteriorating  effects  of  the 
salts  in  sea  water. 

See  Cement,  U  30,  p  933. 

75.  The  disintegration    of  cone    in  water  (salt  or  fresh)  ap- 
pears to  be  due  less  to  action  of  the  water  itself  than  to  the  repeated  action 
of  frost  where  the  cone  is  alternately  exposed  to  freezing  temps  between 
high  and  low  water. 

76.  Mortar  of  puzzolano  and  lime  has  remained  in  perfect  condition  for 
15  to  20  centuries  in  Italian  harbor  works. 

77.  At  the  dock  at  Kobe,  Japan,  to  avoid  possible  injury,  the  salt  water, 
inside  the  dam,  was  replaced  with  fresh  water,  which  entered  at  the  surface, 
while  the  heavier  salt  water  was  pumped  out  from  the  bottom. 

For  Concrete,  see  pages  1084,  etc. 


ABBREVIATIONS.  947  I 

Abbreviations,  symbols  and  references,  in  general  use  in  the 
articles  on  Cement,  Sand   and  Mortar,  pp  930-947  k,  and  on 

Concrete  pp  1084-1210. 
For  references  to  specifications,  see  pp  1184-5. 

agg aggregate 

A  S  T  M American  Society  for  Testing  Materials 

ASCE American  Society  of  Civil  Engineers 

Assn  Eng  Socs.  .  .Association  of  Engineering  Societies 

cem cement 

cone concrete 

constr construction 

c  c cubic  centimeter 

d day 

elas elastic 

E  N Engineering  News 

E  R Engineering  Record 

expt experiment 

h,  hr hour 

Instn  C  E Institution  of  Civil  Engineers 

Jour Journal 

kg kilogram 

km kilometer 

m meter 

mm millimeter 

mo month 

mod modulus 

mom moment 

nat natural 

Port Portland 

Procs Proceedings 

reinfd reinforced  . 

reinfmt reinforcement 

specf  n specification 

standd standard 

surf surface 

T&M Turneaure  and  Maurer,  "Principles  of  Reinforced  Con- 
crete Construction,"  1907. 

T&T Taylor  and  Thompson,  "Concrete,  Plain  and  Reinforced," 

1905. 

Trans Transactions 

transv transverse 

U.  S.  A Report,  Chief  of  Engrs,  U.  S.  Army. 

wk .  .week 

/ per 

U square 

G" square  inch 

> greater  than,  more  than 

< less  than 

> not  more  than,  equal  to  or  less  than. 

< not  less  than,  equal  to  or  greater  than,  at  least. 


1084  CONCRETE. 

CONCKETE. 

For  Cement,  Sand  and  Mortar,  sec  pages  930,  etc. 

For  abbreviations,  symbols  and  references,  see  p  947  I. 

AGGREGATES.* 

Constituents. 

1.  Order  of  value.     (1)  Trap,    (2)  granite,    (3)  gravel,    (4)  marble, 
(5)  limestone,  (6)  slag,  (7)  sandstone,  (8)  slate,  (9)  shale,  (10)  cinders. 

2.  The  strath  of  cone,  with  good  sandstone,  is  about  0.75  X  strength 
with  trap.     With  slate,  less  than  half  strength  with  trap.     Good  cinders 
nearly  equal  to  slate  and  shale.     Hardness  of  agg  increases  in  importance 
with  the  age  of  the  cone  "because,  as  the  cem  becomes  hard,  there  is  greater 
tendency  for  the  stones  themselves  to  shear  thru,  and  the  hardness  of  the 
agg  thus  comes  into  play."     (Sanford  E.  Thompson,  E  R,  '06/Jan/27,  p  109.) 

3.  The  choice  of  agg  is  of  course  a  matter  of  cost,  as  well  as  of  strength, 
&c,  of  product.     Thus,  with  gravel  sufficiently   cheap,  as  compared   with 
broken  stone,  it  may  be  economical  to  use  the  gravel,  or  a  mix  of  gravel  & 
stone,  obtaining  the  reqd  total  strgth  by  Using  a  larger  mass  of  cone.     In 
foundations,  on  weak  ground,  this  is  advisable  because  it  distributes  the 
load  over  a  greater  area. 

4.  In    many  cases,  the    choice  of  sand  and  agg  depends  largely  upon 
what  material  can  be  had,  and  upon  its  distance  from  the  work. 

5.  Where  cem   is   cheap,  it  may  be  economical  to  use  materials  nearest 
at  hand,  and  to  depend,  for  quality,  upon  excessive  use  of  cem. 

6.  Stone  which  breaks  into  nearly  cubical  fragments  packs   better   than 
that  which  splinters  into  long  pieces,  and    the  fragments  are  less  apt  to 
break  in  the  finished  work. 

7.  Good  broken  stone  is  usually  preferred  to  gravel.      The    roughness 
of  the  stone  particles  is  believed  to  give  better  adhesion.     Gravel  cone 
cannot  well  be  tooled. 

8.  Cinders  are  sometimes  used  for  the  agg.     They  are  ordinarily  those 
resulting  from    the    burning    of    bituminous    coal  under    boilers.     The 
material  is  mostly  a  fine  ash,  containing  considerable  unburned  coal. 

9.  Anthracite    cinders  are  less  extensively  used,   the    supply  being 
less  abundant. 

10.  Cinder    cone,  weighing  only  from    80  to  100  Ibs  per  cu  ft,  is  of 
advantage  where  lig'htness  is  reqJ.     Broken  stone  or  gravel  cone  weighs 
from  140  to  145  Ibs  per  cu  ft. 

11.  Clay  or  loam,  adhering  to  gravel  particles,  destroys  or  weakens 
the  adhesion  of  the  mortar  to  the  stones.     The  Boston  Transit  Commission, 
Report  for  1901,  page  39,  found  the  ratio  of  strength,  betw  cone  with  clean 
and  dirty  gravel,  about  60  :  45. 

See  "Clay  and  Loam,"  under  "Sand"  and  "Accidental  ingredients," 
p  1135. 

Size. 

12.  In  beams,  arches,  &c,  the  size  of  aggregate  should  not  exceed 
1.5  to  2  ins  on  any  edge;    but,  if  it  is  well  freed  from  dust  by  screening 
or  washing,  and  if  the  mortar  completely  fills  the  voids,  all  sizes,  from  0.5 
to  4  ins.  on  any  edge,  may  be  used  in  mass  work,  as  foundations,  dams, 
piers,  etc. 

13.  With  large  agg,  coarse  sand  should  be  used,  and  vice  versa. 

14.  It  is  usually  economical  of  cem.  to    screen  sand  from  gravel,  or 
fine  material  from  crusher  stone,  and  then  remix  in  the  required  propor- 
tions. 

Density. 

15.  When  a  solid  body  is  reduced  to  a  mass  consisting  of  broken  pieces 
separated  by  voids,  the  increase  in  bulk  is  due  solely  to  the  voids,  and  is 

*  By  "aggregate,"  we  mean  the  solid  materials  of  cone,  other  than  the 
cem  and  sand.  The  term  "aggregate"  is  sometimes  used  as  including  the 
sand  also. 


PLAIN    CONCRETE.  1085 

equal  to  the  space  occupied  by  them.  Hence  the  ratio,  betw  the  increase 
of  bulk,  or  •'  swelling,"  and  the  original  bulk,  is  that  of  the  voids 
to  the  original,  and  not  to  the  final  bulk.  Thus,  if  a  solid  cu  yd  of  stone, 
after  being  broken  into  pieces,  occupies  twice  as  much  space  as  before, 
then  the  increase  in  bulk,  or  the  space  occupied  by  the  voids,  is  =  that 
occupied  by  solid  pieces  =  half  that  occupied  by  the  entire  broken  mass. 

16.  In  sharp  and  angular  broken  stone,  having  all  its  pieces    of    nearly 
uniform  size,  about  50    per  eent  of  the  vol,  when  measured  loose,  will 
be  voids.     If  the  sizes  of  the  stones  vary  betw  somewhat  wide  limits, 
as  from  2  ins  down  to  %  inch,  the  vol,  occupied  by  the  voids,  will  be  less,  often 
as  little  as  from  28  to  30  %  of  the  whole. 

17.  Tests  by  Mr.  Wm.  Hall  (Trans  A  S  C  E,  Vol  42,  1899,  p  132)  of  voids 
in  crushed  Green  River  blue  limestone,  2.5  inch,  screened;    very  clean  Ohio 
River  gravel,  1.5  inch,  and  mixtures  of  the  two,  resulted  as  follows: 
Percentage  of  stone...  ..100         80         70         60  50  0 

"   gravel 0         20         30         40  50         100 

"    voids 48         44         41         38£         36  35 

These  are  ays  of  a  number  of  tests  of  several  bargeloads  of  materials, 
but  there  was  little  variation  betw  the  mixtures. 

18.  Stone  Crushers.     See  Price-list,  p  992. 

Cyclopean  Concrete. 

19.  "Cyclopean"    cone,  consisting    of  large,    rough    stones  ("dis- 
placers"  or  "plums")  laid  in  cem  mortar,  is  largely,  economically  and  ad- 
vantageously used  in  mass  work,  especially  in  dams,  where  wt  and  hot 
shearing  strgth  are  desiderata.     The  stones  need  not  be  flat.     They  are 
usually  dropt  into  the  wet  mortar,  without  other  bedding  than  that  due 
to  their  fall  and  wt.     Wet  cone  facilitates  the  bedding  of  the  stones,  and 
bonds  better  with  them  than  does  dry  cone. 

20.  At  Chaudiere  water  power  dam,  Canada,  the  "plums"  were 
obtained  from    hard  ledges  in  the  river  bed,  in  good  shape  for  bedding. 
Their  agg  vol  av'd  betw  25  and  30  %  of  the  vol  of  the  dam;    max,  40  %. 

21.  At  Transmere   Bay  Development  Works  (Procs  Inst  C  E,  Vol  171, 
1908,  p.  145)  the  "plums     were  of  sandstone,  9  ins  apart  hor'y.     Near  the 
bases  of  the  walls,  they  weighed  a  ton  or  more.     The  proportion  of  plums 
decreased,  with  wall  thickness,  from  10  to  7  %  of  the  whole  mass. 

22.  Unnecessary    restrictions,  imposed    upon  contractors,  may 
eliminate  the  profit  due  to  the  use  of  "plums."     See  H  19. 


1 086  CONCRETE. 

P:LAI:N  CONCRETE. 

1.  Cement  Concrete  is  composed  of  broken  stone,  gravel,  cindera, 
slag,  shells,  or  other  hard  and  inert  *  material  (the  aggregate),  held  together 
by  cement  mortar,  composed  of  cement  and  sand. 

Advantages. 

2.  The  principal  advantages  of  cone  are   the   convenience  with 
which  it  may  be  placed,  particularly  in  otherwise  difficult  situations  or 
under  water;     its   availability   for   subaqueous  work;     its   cheapness,   due 
largely  to  convenience  of  placing  and  to  its  use  of  stone  too  small  for  masonry; 
and  its  fire-resisting  qualities,  as  compared  with  limestone  (which  calcines) 
and  with  granite  (which  splinters). 

3.  The  availability  of  C9nc  has  been  very  greatly  extended  by  the  practice 
of  reinforcement,  which  permits  its  use  (heretofore  often  impracticable "> 
in  members  subject  to  tension  as  well  as  to  compression,  as  in  beams,  in 
cantilevers    (including    dams     and    retaining   walls),    in    columns,    and    in 
arches  where  the  rise  is  either  very  great  or  very  small,  relatively  to  the 
span.     Reinforcement  permits  the  use  of  much  lighter  sections  than  would 
have  been  safe  when  use  was  made  only  of  the  compressive  strength  of  the 
material. 

For  reinforced  concrete,  see  p  1110. 

4.  Disadvantages.     Cone  is  rather  weaker  than  good  rubble  masonry. 
and  has  only  about  half  the  strength  of  first  class  ashlar  masonry  of  granite 
with  thin  joints  in  cem.     Like  both  the  stone  and  the  mortar  in  masonry, 
it  is  subject  to  deterioration,  especially  in  sea  water;    but  this  difficulty  is 
being  eliminated  by  the  care  which  is  being  given  to  the  manufacture  of 
cem  and  which  is  fostered  by  its  extensive  use  and  by  the  conduct  of  its 
manufacture  upon  a  large  scale.     As  in  all  human  work,  and  notably  in  the 
laying  of  masonry,  care  is  necessary  in  order  to  secure  faithful  performance, 
upon  which  the  success  of  the  structure  so  intimately  depends.     The  quality 
of  the  finished  work  may,  however,  be  tested  by  borings. 

5.  Cone  is  used  for  bringing'  np  uneven  foundations  to  a  level 
before  starting  the  masonry.     By  this  means  the  number  of  hor  joints  in 
the  masonry  is  equalized,  and  unequal  settlement  is  thereby  prevented. 

<$.  On  railroad  work,  the  use  of  cone  may  obviate  tlie  use  of  der- 
ricks, which  are  a  source  of  interference  with,  and  danger  to,  trains. 

7.  Cone  is  \ised  to  advantage.in  reinforcing  and  protecting  old  stone 
masonry ;  but,  unless  special  precautions  are  taken,  the  two  construc- 
tions are  liable,  in  time,  to  separate,  owing  to  unequal  settlement,  especially 
if  the  ramming  has  not  been  thoro. 

Natural  Cement. 

8.  Natural  cement  is  now  seldom  used  in  cone,  except  in  mass  work 
where  it  is  not  subjected  to  the  wearing  action  of  water  or  frost,  and  where 
early  strength  is  not  reqd.     It  is  suitable  for  footings  and  for  low  retaining 
walls  not  subject  to  serious  vibration. 

9.  In  dams,  breakwaters,  etc,  the  core  is  frequently  of  natural  cement 
cone ;   with  a  substantial  outer  shell  of  Portland  cem  cone. 

Proportions. 

10.  The  proportions  of  cement,  sand  and  aggregate  should 
cheoretically  be  determined,  either  all  by  wt,  or  all  by  measure  in  loose 
condition;    but,  in  practice,  the  cem  is  measured  by  the  number  of  pack- 
ages used  (the  contents  of    the  packages    being    known;    see  "packages," 
under  "Cement")  and  the  sand  and  agg  are  measured  loose. 

*  Without  chemical  affinity  for  other  materials. 


PROPORTIONS.  1087 

"Natural  Mix." 

11.  It  is    customary    to  designate    the  quantities  of  cem,  sand 
and  agg,  in  a  cone,  by  proportions.     Thus:   1:2:4  means  1  part  cement 
to  2  parts  sand    and  4    parts    aggregate.     Such    designation    is    necessary 
in  instructions  to  workmen;  and,  where  the  ranges  of  size  of  the  particles 
are    known,  it  indicates  the  character  of  the  cone.     The  proportions  are 
of  course  governed    by  the    character  of  the  work;    but  it    is  inadvisable 
to  affect  distinctions  between  nearly  similar  classes  of  work. 

12.  Usual  proportions  for  Portland  cement  concrete : 

Exceptionally  massive  work  (leveling  for  foundations,  dams,  breakwaters). 

1  :  1.5  :  8     to     1  :  5  :  10;  with  nat  cem,  1:2:5. 
Foundations,  ordinarily,  1:3:6;   sometimes  as  poor  as  1  :  4  :  8. 
Piers,  pedestals,  abutments,  1  :  2.5  :  5.5     to     1  :  3.5  :  7. 
Piers  and  vaulting  in  filters,  1  :  2.5  :  5.5. 

Reinforced  walls  and  beams,  1:3:6;  light  sections,  1  :  2.5  :  5. 
Foundation  walls,  1  :  2.5  :  5.5;    retaining  walls,  1  :  2.5  :  5.5     to     1:3:  6. 
Spandrel  walls,  1:3:6. 

Conduits,  drains,  sewers,  1  :  2.5  :  5.5     to     1:3:6. 
Reservoir,  filter  and  tank  walls,  1  :  1.5  :  3.5     to     1  :  2.5  :  5.5. 
Subaqueous  work,  1  :  2  :  3. 

Floor  systems  (girders,  beams,  slabs)  1:2:4     to     1  :  2.5  :  5.5. 
Stairways  and  roofs,  1  :  2  :  4. 
Arches,  1  :  2.5  :  5;  light  sections,  1:2:4. 
Copings  and  bridge  seats,  1:1:2     to     1:2:4. 

But  the  essential  requisite  is  that  all  the  voids,  between  the  particles 
of  sand  and  agg,  be  filled  with  cem  mortar.  Hence,  unless  the  grading 
of  sizes,  of  sand  and  of  agg,  is  known  or  assumed,  the  bare  statement  of 
proportions,  of  cem,  sand  and  agg,  in  a  mixture,  gives  but  little  useful 
information  as  to  the  value  of  the  cone. 

13.  In  reinforced  work,  in  general,  richer  mixtures  should  be  used 
than  those  that  would   be  permissible  in  large  mass  work.      In  order  to 
obtain  proper  and  reliable  adhesion,  which  is  of  the  first   importance,  the 
bars  must  be  completely  surrounded  by  cem. 

Materials  Required. 

14.  Materials  required  for  a  cu  yd  of  rammed  Portland 
cement  concrete,     c  =  cement,  bbls;    s  =  sand,  cu  yds;     a  =  aggre- 
gate, cu  yds.     Dust  screened  out.     Stones  not  larger  than  1  inch. 


ixti 

z 

ire 
4  

c          s          a 
1  46     0  44     0  89 

2 

5.5  
5  

1.19     0.46     0.91 
1.11     0  51     085 

0 

6 

1  01     0  46     0  92 

n 

4 

7  

7 

0.91     0.42     0.97 
0  83     051     0  89 

4 

8... 

,  .  .  0.77     0.47     0.93 

With  2.5  inch  stone,  the  quantities  of  all  the  materials,  per  cu  yd  cone, 
were  increased  from  2  to  5  %.  With  gravel,  >  %  inch,  they  were  decreased 
about  9  %.  (Chas.  A.  Matcham,  Natl  Builders'  Supply  Assn,  1905.) 

15.  Let 

B  =  No.  of  barrels  of  cement  reqd  per  cu  yd  cone 

=  No.  of  times  0.141  cu  yd  cement  reqd  per  cu  yd  cone; 

P  ==  parts  of  sand  (or  agg)  to  1  part  cem. 

Then 

l/B  =  No.  of  cu  yds  cone  from  1  bbl  cem; 
0.141  P      =  No.  of  cu  yds  sand  (or  agg)  to  1  bbl  cem; 
0.141  PB  =  No.  of  cu  yds  sand  (or  agg)  to  1  cu  yd  cone 


1088 


CONCRETE. 


Void*.     See  Weight,  p  1103. 

16.  Reduction  of  voids.     If   stone  having  50  %  voids,  and  sand 
having  50  %  voids,  be  used,  with  cem,  in  the  proportions: 

Cement,  1  part    =  0.25  cu  yd 

Sand,       2  parts  =  0.50  cu  yd 

Stone,      4  parts  =  1.00  cu  yd 

the  resulting  cone  will  measure  something  more  than  1  cu  yd,  and  yet  it 
will  contain  unfilled  voids. 

17.  These  proportions,   however,   are   not  economical      By  selecting  a 
sand  having  a  range  of  size,  or  by  mixing  two  or  more  sands  having 
grains  of  diff  sizes,  the  voids  in  the  sand  can  be  reduced  to  say  33  %.    Simi- 
larly, the  voids  in  the  stone  can  be  reduced  to  say  35  %.     We  should  then 


y 
have,  say: 


to  say  35  % 

Cement,  1  part  =  0.12  cu  yd 
Sand,  3  parts  =  0.36  cu  yd 
Stone,  8  parts  =  1.00  cu  yd, 


with  results  as  good  as  with  the  1:2:4  mixture  above,  although    using 
only  half  as  much  cement. 

18.  Mr.  Geo.  W.  Rafter  (Trans  A  S  C  E,  Dec,  1899,  Vol  42,  p  106)  recom- 
mends that  the  proportions  be  stated  by  means  of  the  ratio  of  the  vol  of 
the  mortar  to  the  vol  of  agg.     Thus:  a  cone  containing  75  vols  of  agg  and  25 
vols  of  mortar,  would  be  a  33>£  %  cone. 

19.  Under  usual  conditions,  the  voids  in  the  agg  should  be  filled 
with  as  rich  a  mortar  as  the  strength  of  the  work  demands.     A  better  cone 
may  result  from  the  use  of  a  lean  mortar  which  fills  the  voids,  than  with  a 
richer  mortar  but  partially  filling  the  voids. 

20.  The  mortar  cannot  be  perfectly  distributed  thru  the  agg,  and  some 
of  the  voids  are  too  small  to  admit  the  sand  grains.     Moreover,  the  mixture 
is  liable  to  disturbance   in  depositing.     Hence,  there  will  be  voids  in  the 
cone-  unless  there  is  an  excess  of  mortar  over  the  measured  voids  of  the  agg. 

21.  In  practice,  the  excess  of  volume  of  mortar  required,  over 
the  measured  voids  in  the  agg,  in  order  to  secure  the  filling  of  the  voids, 
is  usually  from  15  to  25  %  of  the  vol  of  the  voids.     But  by  15  exp'ts  with 
limestone,  Prof.  Baker  found  that  the  voids  were  not  entirely  filled  unless 
the  vol  of  the  mortar  exceeded  the  vol  of  the  voids  by  40  %.     (Table  13  c, 
p  112  b,  Baker's  Masonry  Construction,  1907.) 

22.  Mr.  John  Watt  Sandeman  (Procs,  Instn  C  E,  Vol  121,  p  219,  1895) 
believes  that,  to  insure    watertightness,  the  vol  of  mortar  should 
be  50  %  of  the  vol  of  agg  having  35  %  voids;    or,  excess  mortar  =  43  % 
vol  of  voids. 


r 


l» 


F° 
I 

*« 


100 


100 


80 


20 


Fig  1. 


Diameter,  d,  in  inches. 
Parabola  of  Maximum  Density. 


See  U  23,  p  1089. 


PROPORTIONS. 


1089 


Density.     See  Weight,  p  1103. 

23.  Mr.  Wm.  8.  Fuller  (T  &  T,  p  197)  finds  that  the  greatest  density 

is  obtained,  and  consequently  the  smallest  amount  of  cem  reqd.,  when  the 
agg  and  the  sand  are  so  graded  that  the  percentages,  by  wt,  passing  the 
various  sieves,  are  as  represented  by  the  ordinates  of  the  parabola  in  Fig. 
1,  where  the  abscissas  represent  the  diams,  d,  of  the  openings  in  the  sieves; 
while  the  ordinates  below  the  parabola  represent  the  percentages  passed, 
and  those  above  the  parabola  the  percentages  retained,  by  these  openings 
respectively. 

24.  In  this  parabola    d  =  P2  M ;  where   d  =  a  given   diam;     P  = 
proportion  of  particles  smaller  than  d;    M  ~  max  diam  of  stone  ( =  2  ins 
in  the  Fig). 

25.  Exp's  (Trans  A  S  C  E,  Vol  59,  pp  67,  &c,  1907)  show  that  a  saving 
of  12  %  in  quantity  of  cem  may  be  effected,  and  a  more  impervious  pro- 
duct obtained,  by  thus  grading  the  sizes  of  the  sand  and  agg;   but  the  reduc- 
tion may  sometimes  be  offset  by  the  additional  cost  of  so  grading,  especially 
on  small  work. 

26.  In  the  lining  of  the  tunnel  for  the  Sudbury  aqueduct,  Boston  Water 
Works,  the  proportions  were 


1       cask  of  Portland  cem  as  it  came  fi 

2%  casks  of  loose  sand 

5  H  casks  of  loose  crushed  stone 


the  dealer  =    3.425  cu  ft 

=     7.35    cu  ft 

.  .  =  18.56    cu  ft 


Total 


.  .  29.335  cu  It. 


By  slightly  shaking  the  sand  and  stone,  the  proportions  became  practically 
1:2:5. 

These  29.335  cu  ft  produced  from  20  to  21  cu  ft  cone,  rammed  in  place: 
or  say  38  cu  ft  materials  =  1  cu  yd  cone 

27.  Mr.  Wm.  B.  Fuller  (Natl  Assn  of  Cem  Users,  Procs,  '07,  p  95)  tested 
cone  beams,  30  days  old,  of  1:2:6,  1:3:5,  1:4:4,  1:5:3, 
1:6:2  1:8:0,  (all  1  :  8).  The  strgths  compared  as  in  Fig  2. 


s 
$  vnn 

319 

tupture  Modulus,  Ibs./ 

8  Q  c 
=>  0  &  2 

285, 

*.  — 

209 

x^ 

151 

xx^ 

102 

^^^ 

^^. 

-^"^ 

a 

Aggregate,  Parts. 
Fig  2.     Proportions  ;  strength. 

28.  From  this  it  appears  that,  so  long  as  the  voids  in  the  agg  are  filled 
with  mortar,   the  comp  strength  of  cone  seems  rather  to  increase   than 
diminish  as  the  proportion  of  stone  increases,  and  to  depend  largely  upon 
the  richness  of  the  mortar. 

29.  Proportioning  by  trial  mixtures:    (Wm.  B.  Fuller,  Trans 
A  SCE,  Vol  59,  pp77,  &c).' 

Having  determined  the  particular  sand  and  stone  to  be  used  on  any 
work,  provide  a  strong  and  rigid  cylinder,  such  as  a  short  piece  of  10  inch 
wrought  iron  water  pipe  capped  at  one  end. 

SO.  On  a  piece  of  sheet  steel  or  other  non-absorbent  material,  weigh  out 
and  mix  together  all  the  ingredients,  to  the  consistency  required  for  the 
work.  Place  the  mixture  in  the  cylinder,  tamping  carefully  and  continu- 

C5 


1090  CONCRETE. 

ously,  and  note  the  height  to  which  the  cyl  is  filled.     Before  the  mixture 
has  time  to  set,  empty  and  clean  the  cyl 

31.  Make  up  another  batch,  using  the  same  wts  of  cem  and  of  water  as 
before,  and  the  same  total  weight  of  sand  and  stone,  but  with  a  slightly 
diff  ratio  of  weights  of  the  sand  and  stone. 

32.  Note  the  height,  in  the  cyl,  reached  by  this  second  and  by  subsequent 
mixtures.     The    best  mixture  is  that  which  gives  the    least  height  in  the  cyl, 
provided  that  it  works  well  while  mixing,  and  that  its  appearance  in  the  cyl 
shows  that  all  the  stones  are  covered  with  mortar. 

33.  This  method  enables  the  engineer  to  select  the  best  from  the  materials 
available  in  any  given  case. 

Consistency.     See  also  Mortar,  p  947/. 

34.  Skill  and  care,  in  placing,  and  uniformity  of  consistency  are  more 
mportant  than  the  consistency  itself. 

35.  The  extremes  of   practice  are:    (1)  Cone  with  mortar  about  as 
moist  as  damp  earth;    only  enough  water  used  to  show  on  the  top  surf 
after  prolonged  and  hard  tamping,  (2)  enough  water  used  to  cause  the  cone 
to  quake  when  first  placed,  and  to  allow  only  of  spading  into  place.     The 
proper  consistency  depends  largely  upon  the  character  and  purpose   of   the 
work. 

36.  Dry  cone  is  generally  preferable  in  large  open  work  where  it  can 
be  thoroly  rammed,  and  where  early  strength  is  reqd,  as  in  arch  skew-backs. 
When  thoroly  tamped,  it  develops  much  higher  compressive  strength  at  itg 
early   ages,   and   may  have  somewhat  greater  permanent  strength,    than 
wetter  mixtures;    but  imperfect  tamping  of  such  mixtures  may  result  in 
very  weak  cone,  while  thorough  tamping  may  render  the  work  more  expen- 
sive than  the  increased  strength  will  justify. 

37.  Medium.     Present  practice  favors  the  use,  in  general,  of  mixtures 
wet  enough  to  require  only  spading;   but,  even  in  such  work,  ramming  may 
be  reqd  from  time  to  time  for  occasional  dry  batches. 

38.  Wet    cone    is    more    easily  mixt  with    thoroness,  more  readily  and 
more  cheaply  laid,  and  more  easily  forced  into  the  narrow  spaces  betw 
reinforcing   bars.     It   comes   into   more   perfect   contact    with    the   molds, 
thus  giving  smoother  and   more   nearly  watertight   surf.     It   is   therefore 
generally  preferable  (as  in  buildings)  in  forms  of  complicated  shape,  or  in 
thin  sections,  or  where  smooth  surfaces  are  reqd. 

39.  Wetness  retards  setting,   gives   better  bond    between  successive 
courses,  gives  a  compact  mass  with  less  tamping,  and  provides  the  surplus 
water  reqd   by  absorption  in  wooden  forms.     Wet  cone  is  less  liable  than 
dry  to  injury  by  bad  workmanship;    but  an  excess  of  water  reduces  the 
strgth,  and  increases  efflorescence. 

40.  In  " cyclopean"  cone,  more  "plums"  can  be  used  with  wet  cone, 
which  allows  them  to  settle  down  into  it,  and  which  bonds  better  with  them. 

41.  Mixtures,  wet  enough  to  be  poured  into  the  forms  for  columns 
of  floors,  are  frequently  used. 

42.  The  quantity  of  water  required,  for  a  given  consistency,  is  materially 
reduced  by  wet  weather. 

43.  Water  works  upward  thru  placed   cone.     Hence  a  less  pro- 
portion of  mixing  water  may  suffice  toward  the  end  of  a  day's  work. 

II  A  \I»M  \<i    A  M>    M  I  \  I  \<i. 
Handling  Ingredients. 

1.  In  designing  a  plant  for  handling  and  mixing  cone,  the  quanti- 
ties to  be  handled,  the  areas  over  which  they  must  be  distributed,  the 
facilities  for  procuring  and  receiving  the  raw  materials,  and  the  working 
space  available,  must  be  considered;  and  each  case  will  present  other  factors, 
peculiar  to  itself. 

2.  The  arrangements  of  such  a  plant  are  as  various  in  character 
as  are  the  different  kinds  of  work.     In  general,  these  arrangements  must  be 
specially  designed  for  each  important  work;     and   success   and   economy 
depend  largely  upon  the  excellence  of  the  design  of  the  handling  plant. 


HANDLING   AND   MIXING.  1091 

3.  Materials  may  reach  the  site  by  cars,  boat  or  team.     Be  on  guard 
against  mud  and  dirt  in  bottom  of  vehicle.     Sand  and  agg  may  be  dredged 
from  stream  at  the  site. 

4.  After  reaching  the  work,  the  materials  are  carried  to  the  bins,  by 
carts,   barrows,   small   cars,   dredge  buckets,   or  belt  or  chain  conveyors. 
From  the  bins  they  are  usually  carried  by  gravity,    thru    hoppers,    to  the 
mixer. 

5.  Storing*.    Gem  is  commonly  stored  in  sheds  or  other  warehouses,  and 
is  handled,  separately  from  sand  and  agg,  in  bags  or  bbls,  often  by  means 
of  chain  conveyors. 

6.  For  bringing  the  materials  from  the  bins  to   the    mixers,  and 
the  cone  from  the  mixers  to  the  work,  carts,  barrows  or  small  cars  are  used. 

7.  Where  the  work  covers  a  limited  hor  area,  as  in  the  case  of  a  building, 
or  of  a  pier  or  abut,  the  mixer  need    not   be   frequently  moved,  and 
the  arrangements  for  handling  are  relatively  simple. 

8.  Where  the  work  covers  a  large  hor  area,  as  in  a  slow  nitration  plant, 
or  where  it  crosses  a  valley,  as  in  a  dam;  cable  conveyors,  with  towers,  are  used : 
or  one  or  more  mixing  plants  are  installed  in  central  positions. 

9.  Where  the  work  extends  along  a  line  of  considerable  length,  as  in  walls, 
sewers  or  aqueducts,  a  railway  track,  often  of  broad  gage  and  with  three  or 
more  lines  of  rails,  is  laid  alongside,  and  the  materials  handled  from  derrick 
cars,  often  of  designs  specially  prepared  for  the  work  in  hand. 

10.  The  work  is  facilitated   by  having  the  cars,  barrows,  buckets,  etc, 
of  known  capacity,  so  that  they  may  serve  as  measures  in  proportioning 
the  sand  and  agg.     Thus,  the  cars  may  hold  enough  sand  or  agg  for  one 
batch,  and  may  dump  into  larger  boxes,  each  holding  enough  sand  and  agg 
for  one  batch.     The  cem  is  usually  measured  separately,  by  counting    the 
bags  or  bbls  emptied. 

11.  Where  cars  are  used,  they  may  be  moved  by  locomotive  or  by  cable, 
reaching  the  bins  by  means  of  an  inclined  plane. 

12.  In  the  case  of  a  belt  conveyor,  sand  and  stone,  each  enough  for 
a  batch  or  other  known  quantity  of  cone,  and  afterward  the  cem  for  the  same 
quantity,  are  dropped  upon  the  belt  from  their  respective  bins. 

13.  Commonly  the  measuring-  platform  (or  the  measuring  hopper 
for  batch  machines)  is  placed  directly  over  the  mixer. 

14.  For  max  output,   there  should  be  two  sets  of  measuring  hoppers, 
one  to  be  dumping  into  the  mixer  while  the  other  is  filling. 

For  washing  sand,  see  SAND,  K  34,  p  947a 

15.  Agg  may  be  washed  in  a  revolving  cylindrical  screen,  by  a  jet 
of  water  under  high  pressure. 

16.  Work  is  often  done  at  night  by  means  of  electric  or  other  artificial 
illumination. 

17.  Portable  (flat-car)  cone  mixing  plant.    Two   6X8  tim- 
bers, 58  ft  long,  4  ft  apart,  laid  upon   floor  of  a  34  ft   standard -gage   flat 
car,  their  ends  projecting  1 2  ft  beyond  each  end  of  car,  and  guyed  to  an  ele- 
vated framework  on  center  of  car.     Each  projecting  end  carried  a  2  cu  yd 
hopper.     Sand  and  gravel  were  shoveled  into  this  hopper  and  discharged 
from  it  upon  a  belt  conveyor,  running  hor'y  under  the  hopper  and  then 
upward  to  a  hopper  (3  cu  yds)  15  ft  above  the  car  floor,  over  the  center 
of  the  car.     This  elevated  hopper  discharged  the  sand  and  gravel  into  a 
:5/4  cu  yd  Smith  mixer,  placed  at  the  center  of  the  car.     Cem  supplied  to 
the  mixer  by  hand;    water  from  a  pipe,  laid  along  the  work  and  provided 
with  hose  connections.     A  bbl,  filled  with  water,  was  carried  on  the  elevated 
framework,   to  ensure  a  supply   for  immediate  use.     The  conveyor  belt, 
2  ft  wide,  consisted  of  two  link-belt  chains,  with  a  heavy  double-thickness 
canvas  belt  between  them.     Belt  supported  by  wrought-iron  pipe  cross- 
pieces    18   ins   apart.     The  belt   forms  pockets   between   the  cross-pieces. 
Conveyors,  driven  by  a  9  X  16  inch  single-cylinder  steam  engine,  mounted 
on  one  end  of  the  car.     Average  capacity,  275  cu  yds  per  day.     One  lower 
hopper  was  found  sufficient  to  supply  the  mixer.     (The  Chalmette  Docks 
of  the  New  Orleans  Terminal  Co,  E.  R,  '06/Jul/28,  p  90.) 

18.  In  constructing  works  which  are  circular    in    plan,   the  mixt  cone, 
for  floors,  columns,  girders  and  roof,  may  be  carried  to  the  formn  by  mean: 
of  a  truss  bridge,  spanning  the  work  from  a  central  tower  to  a  track  on  tht 


1092  CONCRETE. 

circumferential  wall.     The  bridge  then  forms  a  revolving1  crane,  carry- 
ing mixers  at  its  outer  end. 

Mixing. 

19.  Oeneral.     Each  sand  grain  should  be  coated  with  cem,  and  the 
mortar  should  coat  every  fragment  of  stone  in  the  agg  and  should  be  evenly 
distributed  thru  the  whole  vol.     The  stone,  if  dry,  should  be  wetted  before 
adding  it  to  the  mortar. 

20.  Thoroness  of  mixing  is  of  the  greatest  importance;    especially 
when  the  cone  is  poor  in  cem  or  of  dry  consistency. 

21.  The  great  strgth  of  the  cone  in  the  Munderkingen  bridge  is  attributed 
to  its  thoro  mixing.     The  materials  were  mixt  2  mins  dry  and  3  mins  wet. 

22.  Variation  in  color  of  mixture  indicates  change  in  the  proportions 
of  the  ingredients. 

23.  See  that  any  cem,  thrown  out  as  defective,  is  replaced  by  good  cem. 

24.  Lifting  concrete.     Where  the  mixing  platform  cannot  be  built 
near  the  level  of  the  top  of  the  structure,  the  cone  may  be  raised  by  a  power 
lift  to  the  proper  level,  and  then  wheeled  on  level  runways.     For  low  lifts 
and  small  quantities,  horsepower  lifts  are  used;    for  higher  lifts  and  larger 
quantities,  a  small  steam  or  gasoline  engine. 

25.  In  some  cases,  the  mixer  and  its  enclosing  frame  are  lifted  bodily 
by  the  derrick  which  supplies  materials,  and  deposits  them  over  or  near  the 
work. 

26.  Hand  mixing  is  inadvisable  and  uneconomical,  except  on  small 
jobs. 

27.  In  hand  mixing,  it  is  usual  to  mix  the  sand  and  cem  dry,  usually 
by  turning  with  shovels  two  or  three  times,  until  the  mixture  is  of  uniform 
color,  and  each  sand  grain  is  coated  with  cem. 

28.  Water  is  then  added,  and  the  mortar  is  mixed  before  the  agg  is  added; 
or  the  agg  may  be  spread  over  the  dry  mixed  sand  and  cem,  or  these  thrown 
upon  the  agg,  and  the  whole  then  wet  and  mixed  by  two  or  more  turnings 
with  shovels,  until  the  water  is  thoroly  incorporated. 

29.  Mixing  the  cem  and  sand  first,  as  above,  reduces  the  total  labor  by 
omitting  unnecessary  manipulation  of  the  agg. 

30.  Weather.     Hand  mixing  should  be  well  protected  against  wind 
and  rain.     Wind  blows  away  the  finest  (and  therefore  best)  of  the  cem, 
and  rain  prevents  proper  (dry)  mixing  of  cem  and  saijd. 

31.  For  the  sub-station  of  the  Brooklyn  Rapid  Transit  Co.,  two  bottom- 
less rectangular  frames  were  provided,  one  of  which  had  a  capacity  of  Yz 
cu  yd,  and  was  first  filled  with  sand.     Seven  bags  of  cement  were  then 
emptied  on  top  of  it,  and  the  mass  was  turned  several  times  by  five  shovelers 
until  the  color  was  uniform.     It  was  then  leveled,  the  other  frame  (1  cu 
yd  capacity)  was  placed  on  top  and  filled  with  broken  stone,  and  water 
was  put  OH  with  a  hose.     The  mass  was  then  turned  four  times,  shoveled 
into  wheelbarrows  and  deposited  in  the  forms. 

32.  With    equal    care,  machine   mixing    gives    better    and    more 
reliable  results  than  hand  mixing,  and  is  more  economical  on  large  work. 

33.  The  output  must  be  carefully  watched,  as  the  accidental 
and  unsuspected  choking  of  a  hopper  may  change  its  character. 

Mixers. 

34.  Mixers  are  of  two  principal  types;  "continuous,"  and  "batch." 

35.  In  continuous  mixers,  the  raw  materials  are  fed  continuously 
into  the  machine  at  one  end,  and  the  mixed  cone  is  delivered  continuously 
from  the  other  end. 

36.  The  gravity  (continuous)  mixer  is  a  stationary  shute  or  trough, 
set  nearly  vert,  and  equipped  with  fixed  projecting  pins  or  baffles,  against 
which  the  material  impinges  as  it  descends,  and  upon  which  the  mixing 
depends.     Water  is  admitted  by  a  spray  pipe,  at  the  top  of  the  shute. 
Power  is  required  only  to  elevate  the  materials  to  the  top  of  the  mixer, 
usually  a  lift  of  about  8  feet. 

37.  Other  continuous  mixers  are  in  the  form  of  open  troughs, 
nearly  hor,  and  having  a  longitudinal  revolving  shaft,  with  screw-like  blades 


MIXERS.  1093 

attached,  which  convey  the  material,  fed  in  at  the  upper  end,  thru  the 
length  of  the  trough,  to  the  lower  or  discharging  end.  Water  is  provided 
by  means  of  perforated  pipes  along  the  sides  of  the  trough. 

38.  Measuring.     Continuous  mixers  require  S9me  means  of  propor- 
tioning the  ingredients  of  the  cone.     Various  automatic  measurers  have  been 
used  to  a  limited  extent.     Sometimes  the  sand,  cem  and  agg  are  spread, 
in  layers,  on  the  platform  of  the  mixer,  and  shoveled  into  the  mixer.     Some- 
times,  dependence  is   placed   upon    assigning,    for   instance,    one   shoveler 
for  the  cem,  three  for  the  sand  and  six  for  the  stone;    but  this  method  is 
much  too  crude  for  most  cases. 

39.  Batch  mixers  deliver  the  cone  in  batches,  the  size  of  which  is 
determined  by  the  capacity  of  the  mixer.     They  have  a  wider  range  than 
gravity  mixers,  and  give  better  control  of  the  proportioning  of  the  ingre- 
dients. 

40.  The  oldest  and  simplest  batch  mixer  consists  of  a  revolving  cubical 
iron  box,  plain  inside,  mounted  on  bearings  at  its  diagonally  opposite  cor- 
ners, and  provided,  on  one  side,  with  a  sliding  gate,  for  admitting  the  raw 
materials   and  discharging  the  cone.     Power   is  applied   thru  gearing  on 
the  shaft.     The  ingredients  may  be  mixed  dry  for  a  number  of  turns,  and 
the  water  then  added  thru  the  hollow  trunions;    or  the  water  may  be  added 
before  any  mixing  is  done.     The  okler  cubical  mixers  had  to  be  stopped, 
both  at  the  time  of  charging  and  when  delivering  the  cone. 

41.  At  Superior  Entry,  Wis.,  the  U.  S.  Govt  used  a  cubical  cone  mixer, 
charging  and  discharging  without  stopping  and  without  variation  of  speed.    It 
was  operated  by  a  7  X    10  inch  vertical  single  steam  engine,  and  turned 
out  a  batch  of  very  perfectly  mixt  cone  in  80  sees.     The  cone  was  plainly 
visible  during  the  entire  process.     (Clarence  Coleman,  Rept  of  Chf  of  Engrs, 
U.  S.  A.,  1904,  Part  IV,  p  3784.) 

42.  In  later  batch  mixers  the  cubical    box    is    replaced    by  a   drum 
(either  cylindrical  or  made  up  of  two  cones),  rotated  by  means  of  a  chain 
on  a  ring  encircling  the  drum,  and  provided  with  vanes  or  blades  fixed  upon  the 
inside.     These  blades  first  carry  up  and  then  drop  the  material,  mixing  it 
by  the  agitation  so  caused.     The  discharge  is  effected,  in  the  Smith  (double 
cone)  machine,  by  tilting  the  machine  (like  a  Bessemer  steel  converter) 
about  its  trunions,  placed  at  cen  of  grav  of  drum;    and,  in  the  Ransome 
(cylindrical  drum)  machine,  by  inserting  a  tilting  trough,  which,  in  the  dis- 
charging position,  catches  the  material  as  it  falls  from  the  blades. 

43.  To  provide  against  break-downs,  extra  parts  should  always 
be  furnished  with  each  mixer. 

44.  Mounting'.     Mixers  are  either  stationary,  or  mounted  on  skids 
or  wheeled  trucks,  with  or  without  steam  engine,  engine  and  boiler,  gasoline 
engine  or  electric  motor. 

45.  The  mixer,  with  its  framing,  is  sometimes  lifted  bodily  from  its  old 
location,  and  deposited  in  a  new  one,  by  a  derrick  or  cableway. 

46.  Wheeled  cone  mixers,  with  revolving  drums,  into  which  the 
ingredients  are  loaded,  and  in  which  they  are  mixt  by  means  of  the  forwd 
'novemt  of  the  vehicle,  have  been  used.      The  motive  force  may  be  given 
by  hand,  by  horse-power  or  by  gasoline    engine;    and   the  relation,   betw 
forward  speed  and  speed  of  rotation,  may  be  regulated  by  gearing. 

47.  Small  hand-power  batch  mixers  are  furnished;    capacity  claimed 
>  450  cu  ft  per  day. 

48.  In  the  choice  of  a  mixer,  reliability,  as  established  by  success- 
ful use,  is  of  prime  importance,  especially  where  continuity  of  work  is  essential. 

49.  Shortage  of  output  may  be  due  to  shortage  of  power  behind 
the  mixer,  as  well  as  to  the  mixer  itself. 

50.  The  mixer  should  be  cleaned  after  each  day's  work. 

PL.ACIXG. 

51.  The  best  cone  may  be  rendered  almost  worthless  by  carelessness  or 
improper  method  in  the  placing. 

52.  When  cone  is  dumpt   from  a  considerable  height,  there 
would  seem  to  be  danger  that  the  even   distribution    of   materials  may  be 
disturbed.     Hence,  if  lowered  in  buckets,  these  should  be  brought  close  to 
the  work  already  done,  before  dumping.     However,  in  the  construction  of 


1094  CONCRETE. 

pone  piers  for  a  bridge  at  Bethlehem,  Pa.,  by  Cramp  &  Co.  (E  R,  '09 /Mar /6, 

£280)  cone  was  delivered,  thru  an  inclined  wooden  shute,  lined  with  sheet 
•on,  at  a  point  vert'y  74  ft  below  the  mixer;    and  the  method  was  found 
to  be  economical,  and  the  cone  uniformly  good,  and  there  was   no  difficulty 
from  separation  of  ingredients. 

53.  In  work  that  will  show,  the  layers  are  usually  restricted  to  about 
6  ins  in  depth,  owing  to  the  difficulty  of  spading  the  face  work  when  the 
layers  are  thicker;    but  in  foundations,  and  in  heavy  work  above  ground, 
if  to  be  faced  .with  masonry,  or  if  appearance  is  not  important,  layers  of 
wet  cone  as  deep  as  2  feet  may  be  used. 

54.  If  the  cone,  after  placing,  is  found  to  be  too  wet,  it  is  better  t-> 
correct  the  trouble    by  placing    drier  cone  upon  it.     When  surplus  water 
is  bailed  out,  some  cem  is  carried  with  it  and  thus  wasted. 

55.  Excessive  lace  spading  brings  up  water  from  below,  and  thit 
washes  cem  from  the  face. 

56.  Works  of  considerable  length,  such   as   dams    and    walls', 
are  commonly  built  in  sections  alternately,  thus:  sees  1,  3,  5,  etc,  are  first 
built  separately,  and,  when  they  have  hardened,  sec  2  is  built  betw  sees  1 
and  3,  section  4  betw  sees  3  and  5,  etc.     The  sides  of  sees  1,  3,  5,  etc,  thus 
serve  as  part  of  the  forms  for  sees  2,  4,  etc.     This  method  facilitates  bonding 
betw  the  sees,  by  means  of  vertical  dove-tail  grooves,  formed,  by  the  molds, 
in  the  sides  of  the  sees  first  built.     The  cone  of  the  remaining  sees,  placed 
later,  enters  and  fills  these  grooves. 

57.  In  freezing  weather,  cone  can  be  laid  in  large  masses  in  water 
or  below  the  ground  surf.     In  excavations,  if  the  ground  water  is  permitted 
to  rise  over  the  work  during  the  night,  it  will  usually  prevent  frost  from  reach- 
ing the  cone. 

58.  At  Chaudiere  water  power  dam,  cone  was  laid  in  temps  as  low  as 
— 2O°  F.     A  mixing  house  was  erected,  and  the  temp,  within,  was  kept, 
by   stoves,    above    freezing.     Materials   were   lowered    into    the    house    by 
derricks  thru  hatchways  in  the  roof.     Water  was  kept  in  casks,  and  kept 
lukewarm  by  steam  jets.     Sand  was  heated  outside  the  house.     Stone,  in 


piles  3  to  4  ft  deep,  was  heated  (but  not  dried)  by  steam  jets  from  a  perfo- 
iles.     After  placing,  the  cone  was  loosely 
the  nozzle  of  a  steam  hose  was  introduced. 


rated  pipe,  passing  under  the  piles.     After  placing,  the  cone  was  Iposely 
sred  with  canvas,  under  which  the 


Forms. 

59.  In  waU  foundations,  the  trench  itself  may  constitute  the  form;   and, 
in  dams  and  arches  of  cone  blocks,   the  first  blocks,  placed  alternately, 
often  serve  as  parts  of  the  forms  for  the  remaining  blocks;    but  ordinarily 
a  considerable  amount  of  timber  framing  is  required.     See  ^  56. 

60.  The  economy  of  the  work  depends  so  largely  upon  the  design 
of  the  forms,  that  it  is  often  advisable  to  modify  the  design  of  the  work 
itself,  or  to  use  more  cone  than  would  otherwise  be  nec'y,  in  order  to  secure 
economy.     The  design  should    be  such  that  commercial  sizes  of  lumber 
may  be  used,  and  with  a  min  of  wasteful  cutting;    and  such  that  the  forms 
may  be  readily  erected  and  removed  with  a  minimum  of  damage  to  them- 
selves and.  no  damage  to  the  work,  and  used  repeatedly.     Where  practi- 
cable, the  forms  are  made  in  sections,  small  enough  to  be  conveniently 
moved  and  handled  separately.     Cutting  is  economically  done  by  power 
saw  benches. 

61.  Even  in  building  work,  where  much  of  the  "centering"  must  be 
built  in  place,  and  where  it  can  be  removed  only  by  taking  it  to  pieces, 
the  lumber  may  be  used  two  or  three  times  before  it  is  discarded.     Where 
the  forms  can  be  assembled  in  panels,  and  these  panels  removed  as  units, 
they  may  be  used  many  times. 

62.  The  requirements  of  different  works,  executed  under  diff  conditions, 
vary  so  widely,  that  no  useful  details,  as  to  the  construction  of  the  forms, 
etc,  except  for   buildings  (see  Ulf  63  etc),  can    be  given  within  the  limits 
at  our  disposal.     The  designer  should  witness  the  removal  of  his   forms 
before  estimating  their  success. 


FORMS. 


1095 


Forms  for  Buildings. 

63.  In  reinfd  building:  construction,  the  forms  are  chiefly  : 

(a)  Column  forms, 

(b)  Beam,  slab,  floor  and  roof  forms, 

(c)  Wall  forms. 

64.  A  typical  column    form,   Figs    1    and   2.     The   boards,  G,  1% 
ins  thick,  are  held  in  place  by  cleats,  H,  1*4  X  5  ins,  and  by  "column 
clips,"  C,  made  of  pieces  4X4  ins,  and  boards,  B,  1  %  X*  5  ins.     These 
"column  clips"  must  be  spaced  to  take  the  pres  due  to  the  cone.     At  the 
bottom  of  a  column  18  ft  high,  they  should  be  >  10  ins,  cen  to  cen.     At. 
the  bottom,  4  boards,  A,  are  used,  to  hold  the  form  in  shape,  and  the  boards, 
G,  are  cut,  on  one  side  of  the  box,  at  F,  2  or  3  ft  from  the  bottom,  to  form 
a  door  (cleats,  on  door,  not  shown),  thru  which  all  rubbish  may  be  brushed. 
The  door  is  then  held  shut  by  the  lower  two  "column  clips,"  and  the  form 
is  filled      Triangular  fillets,  T,  are  used  to  bevel  the  corners  of  the  col. 


Fig  1. 

Fig-s  1  and  2. 


Column  Form. 


65.  Column  forms  should  be  so  designed  that  they  may  be  removed 
without  disturbing  the  forms  for  the  beams  and  girders.  The  col  forms 
may  then  be  bared  for  inspection,  before  being  loaded. 


Fig-  3.     Beam  Form. 


1096 


CONCRETE. 


66.  Typical  beam  or  girder   forms.   Fig  3.     The  forms,  or  beam- 
boxes,  often  miscalled  "centers,"  are  supported,  betw  columns,  by  tempo- 
rary struts  or  shores,  /,  4  X  4  ins,  about  6  ft  apart,  resting  on  wedges,  J, 
and  the  plank  K.       Corbels,  H,  4  X  4  ins,  are  placed  directly  under  the 
bottoms,  G  (1  M  ins  thick)  and  sides,  C  (1  M  ins  thick),  of  the  beam  boxes. 
The  sides,  C,  are  held  together  by  cleats,  E,  1  M  X  5  ins,  2  ft  apart,  to  which 
are  nailed  the  strips,  D  (1  M  X  6  ins),  upon  which  rest  the  ledgers,  B,  2  X  6 
ins,   about  27  ins  apart.     These  support  the  panel  boarding,  A,   1  J4  ins 
thick;    and  this,  in  turn,  supports  the  slabs.     Small  triangular  fillets,   Tt 
in  the  corners  of  the  beam  boxes,  make  the  box  tight  and  give  beveled  cor- 
ners to  the  beam.     Beam  forms  should  be  given  a  slight  camber. 

67.  Typical  forms   for    floors    betw  steel    beams,  Figs  4  to  6,  vary 
with  span  and  load.     The  forms  are  hung  from  the  bottom  flange  of  the 
I-beams,  by  "hanger  bolts,"  A,  Figs  4  and  6,  %  inch  diam,  with  washers 
and  handle  nuts.     These  bolts  secure  the  pieces,  E,  of  2  X  4  or  3  X  4,  upon 


Fig  4. 


Fig  5. 


Figs  4,  5  and  6. 


Fig  6. 

Floor  Forms. 


which  the  boards,  H  H  H  are  supported  by  2  X  6  or  2  X  8  ledgers,  D 
(about  27  ins  c  to  c,  for  %  inch  boards).  Wooden  blocks  or  sticks,  B, 
Figs  4  and  5,  are  sometimes  used  under  the  ledgers  to  reduce  their  depth. 
Short  cone  blocks,  C,  Fig  4,  are  used,  to  keep  the  forms  away  from  the 
lower  flange  of  the  steel  beam.  These  remain  permanently  in  the  work. 
In  order  to  promote  adhesion  betw  the  lower  flanges  of  the  I-beams  and 
the  thin  mass  of  cone  below  them,  the  flanges  are  often  wrapped  with  metal 
lath,  before  the  blocks,  etc,  are  placed. 

68.  Wall  forms  are  usually  made  up  in  panels,  so  that  they  can  be 
used  several  times.     The  panels  are  cleated  together,  and  are  usually  about 
3  X  12  ft.     The  panels  are  kept  at  the  proper  dist  apart  by  separators, 
of  wood  or  cone,  and  are  held  in  place  by  bolts  or  wire  ties.     When  wood 
separators  are  used,  they  must  be  removed  just   ahead   of  the   concreting. 
Cone  block  or  tube  separators  are  sometimes  used.     These  remain  in  the 
wall.     When  bolts  are  used  that  are  to  be  later  withdrawn  and  used  again, 
they  should  be  loosened  by  means  of  a  wrench,  about  24  hours  after  con- 
creting;   otherwise  it  will  be  difficult  to  remove  them. 

69.  In    the    YTiederholdt  system  of    reinfd  cone  wall  construction, 
the  cone  is  deposited  within  small  hollow  tile  blocks,  which  form  the  finished 
exterior  surface,  and  no  wooden  or  other  temporary  forms  are  used.     The 
blocks  are  shaped  to  meet  the  requirements  of  the  work.     Tiling  aad  con- 
creting are  carried  up  simultaneously. 


FORMS.  1097 

• 

70.  To  reduce  the  cost  of  forms  fn  reinfd  building  construction,  columns, 
beams,  slabs,  etc,  may  be  cast  oil  the  ground,  and  afterward  erected 
and  placed  as  desired;    at  the  sacrifice,  however,  of  the  rigidity  due  to  the 
monolithic  character  of  ordinary  reinfd  work. 

71.  Metal    forms.     When    the    structure    is    of    small    and    uniform 
cross  section,  permitting  the  repeated  use  of  the  same  forms,  as  in  sewers, 
conduits,  tunnels,  etc,  the  lagging,  for  the  wooden  forms,  may  be  of  sheet 
metal.     In  tunnels  and  similar  works,  of  considerable  extent,  and   in  small 
ornamental  work,  forms  composed  entirely  of  metal  may.be  used. 

72.  Both    careless    and    over-careful    alignment    are   to   be    avoided. 
Mr.  W.  J.  Douglas  (E  N  '06/Dec/20,  p  646)  suggests  the  allowance  of  "  3/8 
inch  departure  from  established  lines  on  '  finished '  work,  2  ins  on '  unfinished  ' 
work." 

73.  Avoid  fine  detail,  and  detail  with  sharp  angles.     Corners  should 
be  rounded  or  beveled,  to  facilitate  the  flow  of  cone  and  the  removal  of  forms, 
and  to  render  the  corners  less  liable  to  subsequent  injury. 

74.  Wooden  forms,  within  which  the  cone  is  to  be  placed,  should  be 
fairly  watertight,  smooth,  and  of  sufficient  strgth  and  stiffness  to  hold  to 
line  under  the  pres  of  the  green  cone. 

75.  The  forms  are  usually  of  dimensioned  timber,  faced  with  planed 
boards  or  planks.     The  opening  of  joints  betw  the  planks  may  be  partially 
prevented  by  the  use  of  matched  boards  or  of  tongued-and-grooved  plank. 

76.  Mortar,  exuding  thru  open  joints,  leaves  voids  or  stone  pockets  on 
the  surface.     Hence,   in  forms  for  facework,   joints   should  be  made 
tight,  if  necessary,  by  the  use  of  mortar,  putty,  plaster  of  Paris,  sheathing 
paper  or  thin  metal. 

77.  If  the  lumber  is  very  dry,  when  fastened  in  place,  its  swelling,  due 
to  its  absorption  of  moisture,  may  bulge  the  boards  and  produce  unsightly 
work.     In  such  cases,  the  boards  should  not  be  matched,  but  should  have 
their  edges  slightly  beveled,  and  the  sharp  angle  of  the  edges  of  adjacent 
boards  placed    in    contact.     Swelling    will   then    crush    the    edges  rather 
than  bulge  the  board. 

Lumber  for  Forms. 

78.  White  pine  is  best  for  fine  face-work,  and  quite  essential  for  ornamental 
construction  when  cast  in  wooden  forms. 

79.  Spruce,  fir,  Norway  pine  and  the  softer  kinds  of  Southern  pine  are 
more  liable  to  warp  than  white  pine,  but  are  generally  stiffer  and  therefore 
better  for  struts  and  braces. 

SO.  Partially  dry  lumber  is  usually  best.  Kiln  dried  lumber  is  unsuit- 
able, as  it  swells  when  the  wet  cone  touches  it.  In  very  green  lumber, 
especially  Southern  pine,  the  joints  are  apt  to  open.  Green  lumber  is  heavy, 
and  does  not  hold  nails  well. 

81.  For   wall-panel    forms,    tongued-and-grooved  or  bevel-edge  stuff    is 
preferable    to   square-edge.     Tongued-and-grooved  gives  smoother  surface 
and  less  opening  of  joints,  than  square  or  bevel  edge,  but  is  more  expensive, 
owing  to  waste  in  dressing,  and  there  is  more  wear  at  joints  if  the  forms  are 
used  often. 

82.  Even  for  rough  forms,  planing  on  one  side  may  save  money  by  re- 
ducing the  cost  of  cleaning  after  using.     Studs  should  always  be  planed  on 
one  side,  to  bring  them  to  size. 

83.  Thickness.     For  ordinary  walls,  1  Yi  ins;  for  heavy  construction, 
using  derricks,  2  ins.     For  floor  panels,  1  inch  boards  are  most  used;  but, 
in  tall  buildings,  they  become  much  worn,  and  give  bad  finish  to  under  sides  of 
floors.     For  sides  of  girders,  1  inch  or  1  %  inch  answers,  but  2  inch  is  better 
for  bottoms.     Col  forms  usually  of  2  inch  plank. 

84.  Studding  is  usually  from  3  X  4  to  4  X  6  inch;  4X4  inch  is  the  most 
useful  size.     Spacing,  usually  2  ft  for  1  inch  boards,  4  ft  for  1  %  inch,  5  ft 
for  2  inch. 

85.  Since  beams  and  columns  sustain  greater  stresses  than  floor  slabs, 
their  forms  should  be  left  in  place  longer,  and  should  therefore  be  indepen- 
dent of  the  slab  forms. 

86.  Sides  of  beam  forms  should  be  clamped  or  wedged  together,  to  pre- 


1098 


CONCRETE. 


vent  their  springing  away  from  the  bottom  boards,  under  the  pressure  of 
the  cone. 

87.  Hardwood  wedges,  at  tops  and  bottoms  of  struts    facilitate  the 
setting  and  removing  of  the  struts,  and  testing  for  deflection. 

88.  I.iu lit  Joists  (say  2  X  8  or  2  X  10),  with  frequent  shores,  are  prefer- 
able to  heavier  sizes,  difficult  to  handle. 

Strength  of  Forms. 

89.  The  strength,  required  for  the  forms,  may  be  estimated,  where 
wet  cone  is  used,  by  assuming  the  pres  of  the  cone  as  equal  to  that  of  a  liquid 
weighing  about  150  Ibs  per  cu  ft.*     If  dry  and  hard-rammed  cone  be  used, 
the  wedging  of  the  stone,  due  to  the  tamping,  will  considerably  increase  the 
pressure. 

90.  Permissible  loads,  in  Ibs,  on  wooden  struts  for  floor  construc- 
tion. 


Unsupported 
length,  ft 


Cross  section  of  strut,  inches 


3  X  4  =  12 

4  X  4  =  16 

6  X  6  =  36 

8  X  8  =  64 

14. 

per 
sq  in 

total 

per 
sq  in 

7OO 

total 

1  1  OflfJ 

per 
sq  in 

QOO 

total 

Q94.OO 

per 
sq  in 

1  1  no 

total 
7O4Oft 

12 

600 

7200 

800 

12800 

1000 

36000 

1200 

76800 

10 

700 

8400 

900 

14400 

1100 

39600 

1200 

76800 

8 

850 

10200 

1050 

16800 

1200 

43200 

1200 

76800 

6 

1000 

12000 

1200 

19200 

1200 

43200 

1200 

76800 

91.  In  timber  beams,  calculated  for  strgth,  the  extreme  fiber  stress 
is  to  be  taken  at  750  Ibs  per  sq  inch. 

92.  Construction  live  load,  liable  to  come  upon  cone  while  setting, 
75  Ibs  per  sq  ft  on  slabs;  50  Ibs  per  sq  ft  in  figuring  beam  and  girder  forms. 
This  includes  weight  of  men,  barrows  filled  with  cone,  and  structural  ma- 
terial piled  on  floor,  but  not  piles  of  cem   sand  or  stone,  which  should  not 
be  permitted  unless  specially  provided  for. 

93.  Floor  forms   should    be   based    upon    allowable  deflection,  rather 
than  upon  strength.     Formula: 

3  W  L3  .  =      bh* 

~  384  El  ''  12    ' 

where 

d     =  deflection,  ins; 
W  =  tctal  load  on  plank  or  timber; 
L    =  distance,  ins,  between  supports; 

E    =  elastic  modulus  of  lumber  used  =  1,300,000  Ibs  per  sq  inch; 
7     =  moment  of  inertia  of  cross  section  of  plank  or  joist; 
b     =  breadth  of  plank  or  joist; 
h     =  depth  of  plank  or  joist. 

In  the  usual  formula  for  deflection  (see  p  480)  1  /384  is  the  coeff  for  beams 
with  fixed  ends,  while  5/384  is  that  for  merely  supported  ends. 
Weight  of  cone,  including  reinforcemt,  154  Ibs  per  cub  ft. 
(Sanford  E.  Thompson,  Assn  Am  Portland  Cem  Mfrs,  Bulletin  13,  1907.) 


Details  of  Forms. 

94.  Too  much  nailing  increases  the  difficulty  of  taking  the  forms  apart 
without  injury.  Wire  nails  can  be  pulled  with  less  damage  to  the  wood  than 
can  cut  nails. 

*  Mr.  W.  J.  Douglas  (E  N,  '06/Dec/20,  p  646)  assumes  that  the  cone  is  a 
liquid  of  %  its  own  weight,  or  75  Ibs  per  cub  ft. 


FORMS.  1099 

95.  Iron  or  steel  wall   ties,  extending  thru  the  wall  and  fastening 
the  forma  in  place,  are  usually  removed  and  used  again,  if  >  J4  inch  in  diam. 
If  >    M  inch  diam,  they  are  usually  allowed  to  remain;  but,  if  their  ends 
reach  to  the  outer  surface  of  the  wall,  they  produce  unsightly  rust  stains. 
To  prevent  this,  the  cone,  surrounding  their  ends,  is  chipped  out,  and  the 
rods  are  cut  off,  back  from  the  surface.     The  holes,  thus  formed,  are  after- 
ward plugged  with  mortar. 

96.  Separators    (patented   by  Wm.   T.  McCarthy,    1  Madison  Ave., 
New  York  city),  molded  of  cem  mortar,  in  the  form  of  hollow  cylinders,  and 
in  lengths  of  4  and  6  ins,  encircling  the  bolts,  are  sometimes  used      After 
the  bolt  is  withdrawn,  the  hole  in  the  cyl  is  filled  with  mortar. 

97.  Forms  are  liable  to  disturbance  by  blows  from  the  cone  bucket,  or 
by  the  running  of  machinery  in  contact  with  the  forms. 

98.  Any  cone,  adhering  to  a  form,  must  be  removed  before  the  form  is 
again  used. 

Adhesion  to  Forms. 

99.  Adhesion  to  forms.     If  the  wood  is  new,  and  if  the  forms  are 
thoroly  wet   before  cone  is  placed,  the  cone,  if  hard,  is  not  apt  to  adhere 
to  the  forms  when  these   are  removed.     If  the  forms  are  to  be  removed 
before  the  cone   is   hard,  they  should,  before  concreting,  be  greased  with 
material  thin  enough  to  flow  and   fill  the  grain  of  the  wood.     Crude  oil, 
linseed  oil,  soft  soap  and  other  lubricating  substances  are  used 

100.  New  work  is  apt  to  adhere  to  old  sticks,  where  cone  has  previously 
adhered,  even  tho  this  has  been  cleaned  off. 

101.  Oil,  applied  to  forms  (to  prevent  their  absorption  of  water  or  to 
facilitate  their  removal,  1  99),  is  apt  to  find  its  way  to  joints  betw  old  and 
new  work,  and  prevent  the  formation  of  a  satisfactory  bond.     Soap  and  soft 
soap  are  of  course  harmless  in  this  respect. 

Removal  of  Forms. 

102.  Premature    removal  of   forms  and    props   has   caused    many 
failures  of  cone  buildings;  but  undue  delay,  in  their  removal,  means  delay 
in  the  work  and  increase  in  the  number  of  forms  reqd. 

1OJ5.  The  French  law  requires  that  test  blocks  and  sample  beams  be 
made  for  every  section  cast.  These  enable  the  engineer  to  judge  intelli- 
gently as  to  the  condition  of  the  actual  work. 

104.  Props  should  be  removed  from  one  beam  or  girder  only  at  a  time, 
and  should   be  at  once  replaced  after  the  forms  for  that  beam  have  been 
removed.     This  permits  the  discovery  and  repair  of  defects. 

105.  The  forms  may  be    removed    earlier   in   warm   and   dry 
than  in  cold  and  damp  weather,  earlier  from  under  light  than  from  under 
heavy  loads,  earlier  with  quick-setting   than   with  slow-setting  cem,  and 
earlier  with  dry  than  with  wet  mixtures.     See  Specifications,  p  1191. 

106.  To  release  the  beam  boxes,  the  posts  may  be  supported  on 
wedges  and  capped.     The  posts  and  caps  should  not  be  removed,  from  more 
than  one  beam  at  a  time.     After  the  beam  boxes  have  been  removed,  the 
posts  and  caps  should  be  replaced   before  removing  the  forms  from  any 
other  beams.     Or,  the  posts  may  be  supported  solidly,  and  capped  with 
a  corbel  forming  the  bottom  and  supporting  the  side-boards  of  the   beam 
boxes.     The   side-boards   may    then    be    removed,    leaving   the   posts   and 
corbels  undisturbed. 

107.  Prying   against    the    cone,    in    removing    the    forms,   may 
injure  it. 

Joints  in  Concrete. 

108.  Difficulty.     In  large  work,  the  joints,  betw  work  done  on  diff  days 
or  even  before  and  after  an  hour's  interval,  are  apt  to  give  trouble,  espe- 
cially where  watertightness  is  reqd. 

109.  Causes.     The  difficulty  appears  to  be  due  partly  to  a  surface  skin 
or  glaze,  on  the  surf  of  the  hardened  cone,  and  partly  to  the  presence  of  oily 
or  dusty  materials,  laitance  or  sawdust,  betw  the  two  surfs.      Oil,  used 
upon  the  forms,  or  saturating  the  clothing  of  the  workmen,  is  apt  to  find  its 
way  to  the  joints.     Sawdust  is  particularly  difficult  to  remove.     The  bond 
is  especially  weak  if  the  older  surf  is  frozen. 

73 


1100  CONCRETE. 

110.  Remedies.     Many  remedies  have  been  proposed,  advertised  and 
used,  but  none  has  been  fully  tested  by  time.     See  Specifications,  p  1190. 
Cleanliness  of  surface  and  the  use  of  wet  mixtures  are  probably  the  best 
preventives.     Water,  used  in  scrubbing  joints,  should  be  rinsed  off  with 
clean  water.     A  jet  of  live  high-pres  steam  is  very  effective,  removing  even 
sawdust.     Hydrochloric  acid  is  used  to  advantage.     Patented  methods  of 
securing  bond,  at  joints,  include  the  use  of  metallic  binders,  with  their  ends 
left  projecting  from  the  older  surf,  to  bond  with  the  newer.     Another  method 
employs  a  layer  of  prepared  honey-comb  slag,  sprinkled  over  the  still  soft 
older  surf;  loose  slag  being  removed  after  the  hardening  of  the  older  surf  and 
before  the  placing  of  the  newer  material. 

111.  Where  cone  is  used  in  reinforcing  and  protecting  old  stone 
masonry,  a  stone  should  be  removed  here  and  there  from  the  old  masonry, 
and  the  joints  cleaned  out  and  washed.     Key-bolts,  with  large  washers  on 
their  heads,  may  also  be  driven  into  the  face  and  left  projecting  into  the  con- 
crete.    The  cone  should  also  be  carried  far  enough  down  the  back  of  the 
wall  to  prevent  water  from  working  down  into  the  horizontal  joints  on  the 
tops  of  the  wing  walls  and  main  walls. 

Ramming. 

112.  Ramming  of  cone  is  necessary  only  with  relatively  dry  mixtures. 
When  properly  done,  it  consolidates  the  mass  about  5  or  6  %,  rendering  it 
less  porous,  and  very  materially  stronger.     For  rammers,  see  spec'ns,  p  1189. 
The  men,  using  them,  if  standing  on  the  cone,  should  wear  gum  boots. 

113.  Under  water,  ramming  can  be  done  only  partially,  and  when 
the  cone  is  enclosed  in  bags.     A  rake  may  be  used  gently  for  leveling  loosely 
deposited  cone  under  water, 

114.  Ramming  should  be  discontinued  before  setting  commences.     Ex- 
ramming  disturbs  the  homogeneity  of  the  cone. 


Placing  under  Water. 

115.  Concrete  may  readily  be  deposited  tinder   water   in 

the  usual  way  of  lowering  it,  soon  after  it  is  mixed,  in  a  dredge  bucket,  or  in  a 
V-shaped  box  of  wood  or  plate  iron,  with  a  lid  that  may  be  closed  while  the 
box  descends.  The  lid,  however,  is  often  omitted.  This  box  is  so  arranged 
that,  on  reaching  bottom,  a  pin  may  be  drawn  out  by  a  cord  reaching  to 
the  surf,  thus  permitting  one  of  the  sloping  sides  to  swing  open  below,  and 
allow  the  cone  to  fall  out.  The  box  is  then  raised  to  be  refilled.  In  large 
works  the  box  may  contain  a  cu  yd  or  more,  and  should  be  suspended  from 
a  traveling  crane,  by  which  it  can  readily  be  brought  over  any  required  spot 
in  the  work.  The  cone  may  if  necessary  be  gently  leveled  by  a  rake  soon 
after  it  leaves  the  box.  Its  consistency  and  strgth  will  of  course  be  impaired 
by  falling  thru  the  water  from  the  box;  and  moreover  it  cannot  be  rammed 
under  water  without  still  greater  injury.  Cone  has  been  safely  deposited 
in  the  above-mentioned  manner  in  depths  of  50  ft. 

116.  The  Tremie,  sometimes  used  for  depositing  cone  under  water,  is 
a  box  of  wood  or  of  plate  iron,  round  or  square,  open  at  top  and  bottom, 
and  of  a  length  suited  to  the  depth  of  water.     It  may  be  about  18  ins  diam. 
Its  top,  which  is  always  kept  above  water,  is  hopper-shaped,  for  receiving  the 
cone  more  readily.     It  is  moved  laterally  and  vertically  by  a  traveling 
crane  or  other  device  suited  to  the  case.     In  commencing  operations,  its 
lower  end  resting  on  the  river  bottom,  it  is  first  entirely  filled  with  cone, 
which  (to  prevent  its  being  washed  to  pieces  by  falling  through  the  water 
in  the  tremie)  is  lowered  in  a  cylindrical  tub,  with  a  bottom  somewhat  like 
the  box  described  in  ^[  115,  which  can  be  opened  when  it  arrives  at  its  proper 
place.     When  filled,  the  tremie  is  kept  so  by  fresh  cone,  thrown  into  the 
hopper  to  supply  the  place  of  that  which  gradually  falls  out  below,  as  the 
tremie  is  lifted  a  little  t9  allow  it  to  do  so.     The  weight  of  the  filled  tremie 
compacts  the  cone  as  it  is  deposited.     A  tremie  had  better  widen  out  down- 
ward to  allow  the  cone  to  fall  out  more  readily. 

117.  The  area  upon  which  the  cone  is  deposited  must  previously  be  sur- 
rounded by  some  kind  of  inclosure,  to  prevent  the  cone  from  spreading 
beyond  its  proper  limits;  and  to  serve  as  a  mold  to  give  it  its  intended  shape. 
This  inclosure  must  be  so  strong  that  its  sides  may  not  be  bulged  outward  by 
the  weight  of  the  cone.     It  is  usually  a  close  crib  of  timber  or  plate  iron 
without  a  bottom;  and  will  remain  after  the  work  is  done.     If  of  timber  it 
may  require  an  outer  row  of  cells,  to  be  filled  with  stone  or  gravel  for  sink- 


PLACING.  1101 

ing  it  into  place.  Care  must  be  taken  to  prevent  the  escape  of  the  cone 
through  open  spaces  under  the  sides  of  the  crib  or  inclosure.  To  this  end 
the  crib  may  be  scribed  to  suit  the  inequalities  of  the  bottom  when  the  latter 
cannot  readily  be  leveled  off.  Or  inside  sheet  piles  will  be  better  in  some 
cases;  or  an  outer  or  inner  broad  flap  of  tarpaulin  may  be  fastened  all  around 
the  lower  edge  of  the  crib,  and  be  weighted  with  stone  or  gravel  to  keep  it  in 
place  on  the  bottom.  Broken  stone  or  gravel  or  even  earth  (the  last  two 
where  there  is  no  current),  heaped  up  outside  of  a  weak  crib,  will  prevent  the 
bulging  outward  of  its  sides  by  the  pressure  of  the  cone.  After  the  cone 
has  been  carried  up  to  within  some  ft  of  low  water,  and  leveled  off,  the 
masonry  may  be  started  upon  it  by  means  of  a  caisson,  or  by  men  in  diving 
suits.  Or,  if  the  cone  reaches  very  nearly  to  low  water,  a  first  deep  course 
of  stone  may  be  laid,  and  the  work  thus  brought  at  once  above  low  water 
without  any  such  aids. 

118.  Tlie  concrete  should  extend  out  from  2  to  5  ft  (according 
to  the  case)  beyond  the  base  of  the  masonry.     All  soft  mud  should  be  re- 
moved before  depositing  cone. 

119.  Bags  partly  filled  with  concrete,  and  merely  thrown  into 
the  water,  are  used  in  certain  cases.     If  the  texture  of  the  bags  is  slightly 
open,  a  portion  of  the  cem  paste  oozes  out,  and  binds  the  whole  into  a  tolerably 
compact  mass.     Such  bags,  by  the  aid  of  divers,  are  employed  for  stop- 
ping leaks,  underpinning,  and  various  other  purposes,  that  may  suggest 
themselves.     Such  bags  may  be  rammed  to  some  extent. 

120.  Tarpaulin  may  be  spread  over  deep  seams  in  rock 
to  prevent  the  loss  9f  cone;  and,  m  some  cases,  to  prevent  it  from  being 
washed  away  by  springs. 

121.  Concrete,  placed  in  water,  should  be  in  large  batches,  in  order 
that  the  ratio  of  exposed  surface  to  vol  may  be  small.     In  running  water, 
lead  off  the  flow  in  pipes  or  shutes  or  by  means  of  bulkheads  (for  which  bag 
cone  is  suitable).     If  water  is  pumped  out  of  the  pit  while  concreting,  it  is 
apt  to  take  cem  with  it.     Observe  the  water  flowing  from  the  pump  for  in- 
dications of  loss  of  cem. 

132.  Cone  dock  foundation  on  rock  14  to  19  ft  below  low  water  and 
covered  with  mud.  Laid  with  assistance  of  diver.  Mud  washed  off  by 
jet.  Rock  not  leveled,-  Wooden  forms  built  on  rock.  Spaces,  under  forms, 
filled  with  bags  of  cone.  Forms  held  down  by  means  of  boxes  loaded  with 
broken  stone,  anchored,  by  wire  cables,  near  bottom,  to  neighboring  piles, 
and  braced,  at  top,  by  cross  pieces  nailed  to  existing  dock.  Cone  lowered, 
by  derrick,  in  Yi  yd  bottom-dump  bucket,  and  dumped  when  close  to  work. 
The  only  cem  lost  is  the  little  which  washes  from  top  of  bucket  load  as 
bucket  is  submerged.  The  work  has  smooth  faces  along  the  forms,  and  ap- 
pears to  be  perfectly  homogeneous.  (E  R,  '05/Octy21,  p  468.) 

123.  Placing  cone  in  9O  ft  water,  in  shaft,  to  stop  inrush  of  water  at 
bottom  of  shaft.     Cone  fed,  by  hopper,  into  8  inch  screw-jointed  wrought 
iron  pipe,  lower  end  stopt  with  wood  plug  and  resting  on  bottom  of  shaft. 
When  the  pipe  was  rai&ed  slightly,  the  plug  refused  to  move  and  release 
cone.     Pipe   withdrawn,    taken    apart,    and   each   section   emptied.     Plug, 
not  tight,  had  allowed  lowest  section  to  fill  with  water,  which  disintegrated 
the  cone,  leaving,  at  top  of  lowest  section,  a  plug_of  neat  cem,  which  pre- 
vented the  cone,  above,  from  pushing  out  the  wood'pliig  as  intended.     Expt 
repeated,  with  tight  plug.     Inside  the  8  inch  pipe  was  placed  a  1  ^  inch 
pipe,  by  means  of  which  the  wood  plug  was  knocked  out,  allowing  cone  to 
descend.     Rate  regulated  by  changing  dist  of  foot  of  pipe  above  bottom 
of  shaft.     Mass  of  cone,  10  or  12  ft  thick,  deposited.     The  upper  6  or  8  ins 
never  set;  but    the  remainder    appeared    to    be  solid  and    homogeneous. 
(Assn  C  E,  Cornell  Univ,  Trans,  1898,  p  74.) 

124.  In  a  case  where  hollow  iron  piles,  in  clean  sandy  bottom,  were  filled 
with  cone,  some  of  the  mortar  leaked  out,  and  formed,  with  the  surrounding 
sand,  masses  of  cone,  which  adhered  most  tenaciously  to  the  piles;  suggesting 
the   use   of   hollow  piles,  purposely  perforated,   in   their  lower 
portions,  with  small  holes,  thru  which  grout,  poured  into  them,  at  top,  can 
escape  into  the  sand.     (Chas  List,  Jour  Assn  Engg  Socs,  March,  1903,  Vol  30, 
No  3,  p  124.) 

125.  Superior  Entry,  Wis.     Mixer  discharges  into  a  sub-hopper,  with 
a  cut-off  shute,  which  discharges  into  depositing  buckets  on  cars  under  the 
platform.     Upon  reaching  the  work,  the  buckets  are  lowered  into  the  sub- 


1102  CONCRETE. 

merged  molds  by  travelling  derricks.  Each  bucket  is  provided  with  two 
canvas  covers,  in  two  pieces,  quilted  with  sheet  lead,  and  fastened  to  op- 
posite sides  of  the  bucket.  When  in  position,  these  pieces  overlap  at  the 
middle  of  the  buckets,  completely  covering  the  otherwise  exposed  cone. 
When  the  bucket  has  been  set  upon  the  bottom,  it  is  tripped  by  a  specially 
designed  latch,  from  which  a  rope  leads  to  the  derrick  man  on  the  traveller. 
The  canvas  curtains  prevent  washing  of  the  cone.  A  loaded  bucket  weighs 
13,652  Ibs.  Impact  of  loaded  bucket,  upon  cone  already  laid,  seems  t<j 
compact  the  cone  sufficiently.  Discoloration  of  water  by  cem,  during  de- 
scent of  loaded  bucket,  very  rarely  noticed.  (Report  of  Chief  Engr  U.  S.  A., 
1904,  Part  IV,  p  3785.) 

SURFACE  FINISH. 

126.  Upon  the  removal  of  the  usual  wooden  forms,  the  cone  surface  shows 
the  marks  of  the  grain,  knots  and  joints  of  the  lagging.     This  appearance 
may  or  may  not  be  objectionable. 

127.  Plastering  with  cem  mortar  gives  a  good  finish  in  the  interior  of 
buildings,  where  rain  and  frost  cannot  affect  the    plaster;  but  it  usually 
scales  off  when  applied  to  exterior  surfaces. 

128.  Outer  surfaces   may  be   washed  with  thin  cement  grout, 
after  pointing,  where  necessary,  with  cem  mortar.  .  This  should  be  done 
while  the  cone  is  green,  and,  if  possible,  immediately  after  the  removal  of 
the  forms.     A  thin  grout,  composed  of  1  part  Plaster  of  Paris  and  3  parts 
cem,  applied  with  whitewash  brushes,  gives  satisfactory  results. 

129.  Cone  surfaces  may  be  tooled  with  the  toothed  axe,  giving  a  variety 
of  effects.     If  picked  when  the  cone  is  somewhat  green,  a  rough  surface  is 
left,  which  shows  the  stone  and  corresponds  to  rough  pointed  stone  work. 
Unless  the  tool  is  sharp,  the  surface  is  injured.     When  the  cone  is  older  and 
harder,  picking  gives  the  effect  of  fine  pointing.     Compressed  air  tools  and 
the  sand  blast  have  been  used  effectively,  the  former  on  parts  of  the  Harvard 
Stadium. 

130.  Facings,  of  specially  prepared  mortar,  are  often  placed 
at  the  same  time  with  the  body  of  the  cone,  by  means  of  a  sheet  metal  form 
or  dam,  set  on  edge.     This  dam  separates  the  facing  from  the  backing;  and 
after  both  facing  and  backing  have  been  brought  level  with  its  top,  it  is 
lifted  out  of  its  place  and  used  again  upon  the  layer  of  work  next  above. 
After  the  form  is  lifted,  the  semi-fluid  facing  and  backing  flow  together, 
uniting  in  the  narrow  space  vacated  by  the  form. 


131.  Facing  should  not  be  richer  than  1  :  3,  unless  for  ornamental  work; 
for  plain  surfaces,  1  :  4.     Too  rich  a  facing,  and  excessive  rubbing,  cause  a 
tendency  to  form  hair  cracks  in  the  surface,  and  are  expensive.     On  Chicago, 
Mil.  &  S.  P.  R.  R.,  in  Chicago,  "the  cem  used  in  putting  a.\l/%  inch  facing  of 
mortar  of  1   Portland  :  2  sand,  on  fairly  heavy  abutments,  amounted  to 
about  9  %  of  the  cem  used  in  the  entire  neat  work." 

132.  "In  the  case  of  a  narrow  wall,  the  speed  of  the  work  is  frequently 
impeded  by  the  inability  to  carry  up  the  facing  fast  enough,  and  in  any  case 
two  or  more  extra  men  are  needed,  to  mix  and  carry  mortar  and  to  attend 
to  placing  the  facing  inside  the  form."     ( W.  A.  Rogers,  R  R  Gaz,  'OO/Jul/6, 
P461.)  

133.  With   spaded    or  mortar   finish,  to    protect  the  work  from 

frost  a  layer  of  tar  paper  may  be  placed  outside  the  studs,  leaving  an 
air  space,  of  the  thickness  of  the  studs,  betw  the  paper  and  the  lagging.  In 
this  space,  the  temp  will  be  from  8°  to  10°  above  that  of  the  outside  air. 
Such  a  protection  is  of  course  most  needed  on  the  sides  exposed  to  the  wind. 
(W.  J.  Douglas,  E  N,  'OG/Dec/20,  p  650.) 


134.  Change  of  hands,  during  the  progress  of  finishing  work,  may  result 
in  loss  of  uniformity  of  appearance. 

135.  Scrubbing  before  cone  is  set.     Mr.  U.  H.  Quimby  (Natl 
Cem  Users  Assn,  Procs,  1907)  scrubs  the  fresh  cone  surf,  before  hard  set, 
with  a  brush  and  water,  thereby  removing  the  film,  and,  with  it,  all  impres- 


PROPERTIES.  1 103 

sion  of  the  forms,  and  exposing  the  clean  stone  and  sand  of  the  cone.  A  few 
rubs  of  an  ordinary  house  scrubbing  brush,  with  a  free  flow  of  water  to  cut 
and  to  rinse  clean,  suffice;  but  a  little  additional  rubbing  improves  the  effect. 
The  necessity  for  early  removal  of  the  f9rms,  when  this  method  is  used, 
necessitates  special  care  in  their  construction,  increasing  their  cost.  When 
applied  to  surfaces  forming  square  corners,  the  projecting  sand  particles 
produce  a  ragged  effect.  Hence  care  should  be  taken  not  to  extend  the 
treatment  to  such  corners. 

136.  An  effect  similar  to  that  obtained  by  Mr.  Quimby's  method,  may  be 
produced,  after  hard  set,  by  washing  with  an  acid  solution,  which 
is  afterward  removed  by  the  use  of  an  alkaline  wash,  followed  by  water. 
This  method  attacks  limestone  in  the  agg. 

137.  Color  effects  are  best  produced  by  using  agg  of  the  desired  color. 


138.  The  difficulty  of  making  oil  paint  adhere  to  fresh  cone 
surfs  is  due  to  moisture  and  free  lime.  A  wash  of  dilute  acid  neutralizes  the 
lime,  but  is  unsatisfactory,  muriatic  (hydrochloric)  acid  forming  highly 
hygroscopic  salts,  such  as  calcium  chloride,  and  sulfuric  acid  having  only  a 
superficial  effect.  Dissolve  10  Ibs  ammonia  carbonate  (salts  of  hartshorne) 
in  45  gals  water,  and  apply  once  with  a  brush,  or  give  several  coats  of  a 
weaker  solution,  or  apply  as  spray.  The  ammonia  is  liberated,  and  the 
carbonic  acid  forms,  with  the  free  lime,  an  insoluble  carbonate,  which 
soon  becomes  dry  and  hard.  After  exhaustive  trials,  this  was  found  the 
only  method  which  satisfies  every  requirement.  The  amm  carb  keeps,  for 
any  length  of  time,  in  fairly  tight  vesesls.  (Fred  J.  Bosse,  "Cement 
Age,"  '09 /Jan,  p  48.) 


PROPERTIES  OF  CONCRETE. 

Weight.     See  Voids,  p  1088,  and  Density,  p  1089. 

1.  Weights  of  concrete,  in  pounds  per  cubic  foot. 
Broken  stone  or  gravel  concrete,  130  to  160;  ordinarily  140  to  150.* 

One  foot  B  M  =  vol  of  a  solid  1  ft  square  and  1  inch  thick,  =  144  cu  ins  = 
1  cu  ft/12. 

144  Ibs  per  cu  f t  =  1  Ib  per  12  cu  ins  =  1  Ib  per  prism  1  inch  square  and 
12  inches  long. 

Hence,  at  144  Ibs  per  cu  ft,  the  wt  of  any  prism  in  pounds  =  area  of 
cross  section  in  square  inches,  multiplied  by  length  in  feet,  =  vol  in  cubic 
inches/12. 

Wt,lbs/cuft 100       110       120       125       130       140       150     160 

Kilograms  /  cu  meter 1600     1760     1920     2000     2080     2240     24002560 

Cinder    concrete, 110  to  120; 

Sandstone    "  143 

limestone    "  148 

Oravel  "  150 

Trap  155 

With  natural  cem,  4  to  5  Ibs  lighter  per  cu  ft 

2.  The  unit  weight  varies  not  only  with  character  of  constituents,    but 
also  with  proportions,  consistency,  degree  of  compacting,  etc. 

Permeability. 

3.  Even  where  the  primary  object  of  the  cone  is  not  the  prevention  of 
percolation  by  water,  impermeability  is  of  great  importance  in  promoting 
the  durability  of  the  cone,  and  especially  in  protecting  metal  reinfmt  from 
corrosion  and  from  loss  of  adhesion  with  the  cone. 

4.  Water  may  pass  thru  cone,  etc,  so  slowly  that  evaporation,  from  the 
outside,  proceeds  more  rapidly  than  the  water  can  reach  it,  so  that  the  out- 
side of  the  wall   may  appear  dry,  altho  percolation  is  actually  taking 
place. 

*144  Ibs  per  cu  ft    =  12  Ibs  per  ft  B  M.  (Board  measure). 
120    "     "     "   "    =  10    "     "  " 
108    "     "     "  "    =     9    "     ' 


1104  CONCRETE. 

5.  When  made  into  hardened  mortar,  well  trowelled  down  on  all  surfaces 
which  come  into  contact  with  water,  neat  cement  is  as  nearly  im- 
permeable as  the  best  of  natural  rocks  used  for  building  purposes-  (Wm. 
B.  Fuller,  Trans,  A  S  C  E,  Vol  51,  pp  133-4,  Dec  1903.) 


6.  Mortar  or  cone,  so  proportioned  as  to  obtain  the  max  practica- 
ble density,  and  mixt  rather  wet,  is  impervious  under  ordinary  conditions. 

7.  Small  blocks  of  cone,  carefully  made  from  materials  so  graded  as  to 
insure  great  density,  or  with  an  excess  of  cem,  have  been  repeatedly  found 
to  be  as  nearly  impervious  as  the  best  natural  stones.     See  Expts,  p  1138. 

8.  In  large  masses,  in  actual  construction,  it  is  difficult  to  produce 
an  absolutely  tight  structure  without  the  addition  of  a  lining  of  material 
more  nearly  impervious  than  the  cone.     Variations  in  the  mixture,  careless- 
ness in  manipulation  or  placing,  or  in  bonding  betw  successive  days'  works 
(an  hour's  interruption,  in  the  middle  of  a  hot  day,  has  been  known  to  cause 
leakage),  or  insufficiency  of  water,  will  render  cone  permeable,  in  spite  of 
proper  theoretical  proportioning  and  the  addition  of  lime.     The  mix  should 
be  at  least  wet  enough  to  settle  into  place  with  but  little  ramming. 

9.  Cone,  impervious  in    itself,  may  develop  cracks  thru  which  water 
may  permeate.     Reinfmt,  properly  placed,  opposes  such  cracking. 

10.  Water  may  permeate  thru  the  mortar,  thru  the  particles  of  agg,  or 
betw  mortar  and  agg.     Probably  most  of  the  percolation  takes  place  thru 
the  mortar.     See  Mortar.     We  here  deal  with  those  aspects  of  permeability 
which  can  better  be  discussed  in  connection  with  the  cone  as  a  composite 
material. 

11.  When  the  leakage  consists  of  mere  percolation  thru  the  minute 
pores  of   cone,  etc  (i  e,  when  there  are  no  actual  fissures),  leakage  gen- 
erally diminishes  with  use,  the  water  (even  when  apparently  clear)  blocking 
its  own  passage  by  depositing,  in  the  pores  of  the  material,  either  its  own 
natural  sediment,  or  (in  the  form  of  "laitance")  lime  and  other  compounds 
dissolved  out  of  the  cone  itself. 

12.  This  action  depends  upon  many  factors,  notably  the  pressure,  the 
sizes  and  shapes  of  the  pores,  the  hardness  and  solubility  of  the  material, 
and  the  character  of  the  sediment  carried  by  the  water.     Thus,  under  high 
pres,  if  the  material  is  easily  scoured,  or  if  the  pores  are  large  and  relatively 
straight,  leakage  may  be  expected  to  increase,  rather  than   diminish,  with 
time. 

13.  Where  the  nature  of  the  case  permits,  as  in  floors,  retaining  walls,  etc., 
it  is  better  to  lead  the  water  off  by  proper  drainage,  than  to  attempt  to 
block  its  passage  by  rendering  the  structure  watertight. 

14.  Where  watertig-htiiess  is  required,  as  in   dams,  the   con- 
stituents must  be  carefully  proportioned  for  max  density,  there  must  be  an 
excess  of  rich  mortar  over  vol  of  voids,  dry  mixtures  should  be  avoided,  the 
mixing  must  be  thoro,  and  the  construction  should  be,  as  nearly  as  possible, 
monolithic. 

15.  The  application  of  waterproofing  materials  may  be  either  (a) 
internal,  mixt  with  the  ingredients  of  the  cone;   (b)  superficial,  filling  the 
pores  near  the  surf;   (c)  external,  preventing  contact  betw  water  and  cone. 

16.  Internal.     For  water  tight  work,  the  vol  of  mortar  should  be  40  to 
45  %  of  the  vol  of  agg,  or  40  to  42  %  if  the  agg  is  graded.     (Geo.  W.  Rafter, 
Trans,  A  S  C  E,  Vol  42,  p  149,  Dec  1899.) 

17.  With  agg  having  35  %  voids,  the  vol  of  mortar  should  be  <  50  % 
of  vol  of  agg;  vol  of   dry  sand    and  cem  <  %  vol  of  agg;    vol  of  sand  > 
2  X  vol  cem.     For  cem  leaving  >  10  %  on  No.  120  sieve,  ordinary  sands, 
and  agg  with  35  %  voids,  the  following  proportions  are  given: 

cem         sand  agg     (sand  +  agg)  -v-  cem 

1  1.0  3.00  4.00 

1  1.5  3.75  525 

1  2.0  4.50  6.50 

See  Plain  Concrete,  If  22,  p  1088. 

18.  Every  particle  of  sand  must  be  coated  with  cem,  and  every  particle 
of  stone  with  mortar,  so  that  the  stones  or  the  sand  grains  do  not  touch. 

19.  To  insure  this  result,  mix  by  means  of  one  of  the  newer  types  of  ma- 


PERMEABILITY.  1105 

chine,  introducing  first  the  measured  quantity  of  water  and  then  the  cem, 
making  a  liquid  grout  which  will  run  easily  into  the  most  minute  voids  of 
the  sand,  which,  being  next  introduced,  becomes  coated  in  the  shortest  space 
of  time.  The  resulting  mortar  is  still  quite  liquid,  and  flows  into  all  the  voids 
of  the  stone.  (Win.  B.  Fuller,  Trans  A  S  C  E,  Vol  51,  p  135,  Dec  1903.) 
For  the  use  of  lime,  see  Expt.  82  a,  p  1177. 

20.  In  making  thin  slabs  with  a  cone  of  2  parts  cem  to  5  of  fine  bitumi- 
nous ash,  reinfd  with  poultry  mesh,  Mr.  W.  K.  Hatt  (Trans,  A  S  C  E,  Vol  51, 
p  129,  Dec  1903)  employed  a  5  %  solution  of  ground  alum,  in  place  of  one  half 
of  the  gaging  water,  and  a  7  %  solution  of  soap  in  place  of  the  other  half. 
This  strengthened  and  hardened  the  ash  cone  by  about  50  %,  and  diminished 
its  absorption  by  about  50  %.     The  soap  solution  alone  diminished  absorp- 
tion, but  did  not  strengthen  the  cone.    Sand  mortar  was  not  greatly  strength- 
ened by  the  soap  and   alum    treatmt,  but  its  absorption  was  dimin- 
ished about  50  %. 

21.  If  joints  are  inevitable,  they  may  be  first  wet,  and  then  covered  with 
neat  cem  paste  or  1  :  1  cem  mortar,  upon  which  the  new  work  is  to  be  placed 
before  the  binding  course  hardens. 

22.  The  permeability  of  cone  linings  of  aqueducts  &c  may  be  diminished 
by   drilling   holes    thru   them   and    forcing  in  grout  behind  them  by 
means  of   grout   pumps.     The    grout  sometimes  appears  at   many  points, 
indicating  that    it   is    passing  not  only  thru  the  cracks  but  also    thru  the 
body  of  the  cone.     This  method  was  successfully  used  in  the   Torresdale 
filtered  water  conduit,  Philadelphia. 

23.  Superficial.     For  plastering  the  inside  of  a  covered  clear  water 
well,  Mr.  Edwd  Cunningham  used  1.25  Ibs  of  soft  soap  for  each  5  buckets  of 
water,  and  3  Ibs  of  alum  per  bag  of  cem.    The  mortar  was  easy  to  handle  with 
the  trowel,  but  had  a  nauseating  odor.     2  coats,  not  more  than  0.5  inch  in 
all.     18-inch  dividing  wall  showed  no  leak  when  one  side  held  16  ft  of  water. 
The  soap  was  made  of  clarified  fats,  and  cost  7.5  cts  per  Ib;  much  too  high. 
With  1  part  cem  to  2  parts  sand,  6  to  9  gals  of  water  and  12  Ibs  of  alum  were 
required  for  each  bbl  of  cem.     (Trans,  A  S  C  E,  Vol  51,  pp  127-8,  Dec  1903.) 

24.  As  an  external  treatment,  Mr.  Richd  H.  Gaines,  New  York  Board 
of  Water  Supply  (Trans,   A  S    C  E,  Vol  59,  p   160,  Dec  1907)  found   the 
Sylvester  soap  and  alum  process  (p   928),  "fairly   effective,   but 
very  expensive  for  large  work. " 

25.  Asphalt   can   be   successfully   applied   only  to   dry   surfaces.     It 
becomes  brittle  and  loses  its  efficiency  upon  oxidation;  but  it  will  often 
prevent   leakage   until   the  structure  has   become   tight    thru   infiltration. 
See  II  11,  p  1104. 

28.  The  cone  surface  must  be  clean,  and  must  first  be  treated  with  a 
thin  wash  of  liquid  asphalt,  thinned  with  benzine.  This  enters  the  pores 
of  the  cone,  and  acts  as  a  binder.  Without  this,  the  asphalt  coating  will  not 
adhere  to  the  cone. 

27.  Asphalt  coatings,  should  be  made  continuous,  and  should  be  pro- 
tected against  decay,  from  creeping  and    from  abrasion,  by  being    placed 
between  alternate  layers  of  cone,  or  by  being  covered  with  brickwork  or 
masonry. 

28.  Tunnels,   subways   and   basements,   below  water   level,   have  been 
thoroughly  waterproofed  by  continuous  layers  of  heavy  roofing  papers, 
well  mopped  with  tar  or  asphalt,  and  placed  between  outer  and  inner  cone 
walls. 

29.  The  two  basins  of  Queen   Lane   reservoir,   Philadelphia,   originally 
lined  with  cem  cone  on  sandy  clay  puddle,  and  holding  383  million  gals  of 
water  30  ft  deep,  were  re-lined  with  Bermudez  asphalt  in  1896-7.     The  floor 
received  2  inches  of  asphalt  cone,  with  a  thin  top  layer  of  hot  liquid  asphalt; 
the  slopes,  two  layers  of  hot  liquid  asphalt,  with  burlap  between  them;  the 
burlap  being  anchored  at  top  by  being  lapped  around  horizontal  iron  or 
wooden  bars,  let  into  the  asphalt' paving.     While  this  work  was  in  progress, 
the  south  basin  of  the  Roxborough  reservoir  (147  million  gals,  25  ft  deep) 
was  similarly  lined.     In  the  north  basin,  Alcatraz  (California)  asphalt  was 
used,  and  the  slopes,  as  well  as  the  sides,  were  treated  with  asphalt  cone. 
All  four  of  these  basins  have  since  been  in  continuous  use,  without  sensible 
leakage. 

C6 


1106  CONCRETE. 


Elastic  Modulus,  E.     See  Iffl  12  and  13,  p  1111. 
en  cone  is  subjected  to 
l  curved  throughout  it 
stress,  per  unit  of  area 


3O.  When  cone  is  subjected  to  compressive  test,  its  stress-strain  diagram 
is  in  general  curved  throughout  its  length;  its  elastic  modulus, 


,.     .    .  ,  . 
,  diminishing  as  the  stress  increases. 


.  , 

shortening,  per  unit  of  length 

Strength. 

31.  Cone  being  weak  in  tension,  and  brittle,  its  tensile  strength  is 

usually  and  properly  neglected:  dependence  is  placed  chiefly  upon  its 
comp  strgth,  and  its  tensile  and  shearing  strgths  are  usually  exprest  as 
fractions  of  the  comp  strgth. 

32.  The  compressive   strength  is  preferably  determined    experi- 
mentally by  means  of  cubic  specimens.     The  unit  comp  strgth  decreases 
when    the   ratio,  length/side,   increases,   and,   in  similar   specimens,   when 
their  dimensions  increase. 

33.  Cone  prisms,  tested  in  endwise  compression,  usually  fail 
by  shearing  on  planes  oblique  to  the  axes  of  the  prisms.     Upon  these  oblique 
planes,  the  unit  shear  is  about  half  the  ult  comp  stress. 

34.  The  strgth  varies  widely  with  the  character  of  the  cone. 

35.  For  12  inch  cubes  of  Portland  cem  mixtures  having  from  6  to  18 
volumes  of  (sand  4-  agg)  to  1  vol  cem,  Mr.  Edwin  Thacher  deduces, 
from  the  data  of  Expt  18  a,  the  straight-line  formula, 

S  =  M  —  N  X 
where 

S    =  ult  comp  strgth,  Ibs  per  sq  inch; 
X    =  No  of  parts  of  sand  to  1  part  cem; 
M  and  N  =  values  as  below: 

Age  =  7  days  1  month  3  months         6  months 

M     =     1800  3100  3820  4900 

N     =       200  350  460  600 

Mr.  Thacher  holds  that,  for  practical  mixtures,  "the  strgth  of  cone  de- 
pends principally  on  the  strgth  of  the  mortar,  and  not,  to  any  great  extent, 
upon  the  amount  of  stone.  "  In  these  tests,  the  vol  of  stone  was  always 
twice  the  vol  of  sand. 

36.  But  few  tests  have  been  made  to  determine  the  tensile  strength 
of  cone.     It  is  usually  taken  as  approximately  from  one-tenth  to  one-eighth 
the  comp  strength,  and  the  shearing  strength  as  from  1.2  to  1.5  times 
the  tensile. 

37.  Prof.  L.  J.  Johnson  (Jour,  Assn  Eng  Socs,  Vol  38,  No  6,  p  310,  June, 
1907)  tested  25  reinfd  beams,  3  ins  X  9  ins  X  8  ft,  loaded  6  ins  from  each 
support;   19  of  the  beams  were  of  1:2:2%  scaly  trap;  6  of    1  :  2.5  :  5. 
All  the  beams    tailed  by  slip  of  reinfmt  :    the   1:2:2%  beams, 
137  to  143  days  old,  successfully  resisted  shears  of  233  to  573  Ibs  per  sq  in; 
av  470;  and  the  1  :  2.5  :  5  beams,  488  to  750;  av  628. 

38.  In  beams,  owing  to  the  rising  of  the  neutral  axis,  under  loading, 
the  ult  unit  fiber  stress,  or  rupture  modulus,  is  about  1.6  X  the  unit 
tensile  strgth. 

Setting. 

39.  Setting  is  of  course  a  function  of  the  cement  paste.     See  Mortar. 
We  here  treat  of  setting,  as  affecting  the  cone  as  a  composite  body. 

40.  Temperature.    In  hot  weather,  cone  sets  very  much  faster  than  in 
cool  weather,  and  the  load  may  therefore  be  applied  sooner  in  hot  weather; 
but  the  time  required  varies  with  the  class  of  structure  and  of  cone. 

41.  Gradual  loading.     Where  the  loading  is  static  or  gradually  increased, 
the  time  may  be  shorter  than  where  the  load  is  applied  suddenly  or  is  sub- 
ject to  impact. 

42.  "As  a  general  rule,  bridge  abutments  and  piers  of  Portland 
cem  cone  should  be  allowed  to  set  at  least  a  month  before  using,  if  built 
during  ordinary  warm  weather.     If  built  during  cold  weather,  their  use 
should,  if  possible,  be  deferred  until  warm  weather  sets  in."   (W.  A.  Rogers, 
RR  Gaz,  'OO/Jul/27,  p  514.) 


BEHAVIOR.  1107 

43.  Steel  girder  spans  have  been  placed  upon  Portland  cem  cone  abut- 
ments without  injury  2  weeks  after  the   completion  of   the  abuts   in    hot 
weather;  but  work  of  the  same  character,  finished  early  in  Dec,  was  found 
not  very  solid  inside,  early  in  the  following  March. 

Effects  of  Heat  ami  Cold. 

44.  Freezing1  nearly  always  damages  nat  cem  mortar  or  cone  to  such 
an  extent  that  it  must  be  replaced  by  new  material. 

45.  With  Portland  cem  cone,  freezing  suspends  the  setting; 

and  hardening  of  the  mortar,  for  the  length  of  time  during  which  the  material 
has  been  frozen.  The  apparent  loss  of  strgth,  in  frozen  specimens,  may  often 
be  due  merely  to  such  delay  in  setting. 

46.  While  freezing  seldom  results  in  material  reduction  of  the  ult  strgth 
of  Port  cem  cone,  yet  it  may  produce  serious  results  by  giving  the 
cone  an  apparent  hardness;  thus  causing  the  premature  removal  of  forms, 
or  the  imposition  of  undue  loads,  which  may  produce  failure  when  the  cone 
thaws  out,  if  it  had  not  already  set  sufficiently  before  being  frozen. 

47.  If,  soon  after    the  mortar,  thru  the  entire  thickness  of  a  wall,  is 
frozen,  the  sun  shines  on  one  face  of  it,  so  as  to  soften  the  mortar  of  that  face, 
while  the  mortar  behind  it  remains  hard,  it  is  plain  that  the  wall  will  be 
liable  to  settle  at  the  heated  face,  and  at  least  bend  outward  if  it  does  not 
fall. 

48.  If  the  freezing  does  not  take  place  until  after  the  cem  has  taken  its 
initial  set,  there  is  little  danger.     Thin  work  should    not  be  done  at  < 
28°  F  on  a  rising,  or  at  <  32°  on  a  falling  temp. 

49.  A  thin  scale  is  likely  to  crack  from  the  surface  of  cone  walks  or 
walls  which  have  been  frozen  before  the  cem  has  hardened.     Granolithic  or 
troweled  finish  sometimes  spalls  up  in  small  patches,  when  frozen. 

Protection. 

50.  Protection    against    freezing1    is    expensive    and    uncertain. 
Hence  the  placing  of  cone  in  freezing  weather  should  be  avoided  when  possible. 

51.  Housing"  and  heating*  the   finished   work.     Tents   or  screens 
may  be  used ;  but  wooden  sheds  are  more  effective. 

52.  Covering1  the  cone,  as  soon  as  placed,  with  canvas,  cem  bags  or  tar 
paper,  or  with  a  thick  layer  of  sand,  straw,  manure,  sawdust  or  other  poor 
heat-conductors.     Straw  should  be  <  1  foot  deep.     Manure  is  the  best,  but 
it  discolors  the  work.     Canvas  etc  should  be  kept  an  inch  or  two  away  from 
the  cone,  leaving  an  air  space.     Otherwise  use  two  layers. 

53.  Heating1  the  materials.     Stone  is  frequently  heated  by  piling  it 
over  a  pipe  or  improvised  oven,  and  building  a  fire  inside;  or  over  a  coilof 
pipe  containing  numerous  small  holes,  and  then  forcing  steam  thru  the  pipe. 
The  cone  must  be  used  before  the  steam  is  condensed  and  frozen.     Sand  is 
heated  over  a  long  sheet  i'-on  stove. 

54.  Lowering-  the   freezing  point  of  the   mixing-  water, 
by  the  addition  of  chemicals. 

55.  Salt  is  the  cheapest  and  most  commonly  used  material.     It  lowers 
the  freezing  point  about  1 .5°  F  for  each  1  %  salt  added  to  the  water.     A 
10  %  solution  (12  Ibs  salt  per  bbl  of  cem)  reduces  the  freezing  point  to  17°  F 
and  does  not  injure  the  strgth  of  the  cone.     For  32°  F,  dissolve  1  Ib  salt  in 
18  gals  water;  add.3  oz  salt  for  each  3°  below  32°  F.     (Ch  of  Engrs,  U.  S.  A. 
Report,  1895.)     Larger  percentages  of  salt  appear  to  weaken  the  cone. 

5H.  Calcium  chloride,  15%  solution,  or  1.25  Ibs  per  gal  of  water, 
lowers  the  freezing  point  to  about  20°  F,  and  does  not  weaken  the  mortar. 
It  rapidly  absorbs  moisture,  and  it  is  possible  that,  if  ground  dry  with  the 
Portland  cem  clinker,  even  to  the  amount  of  0.5  %,  it  would  cause  the  ma- 
terial to  gather  dampness.  The  chloride  dissolves  with  extreme  rapidity, 
and  may  be  added  to  the  mixing  water.  (Prof.  R.  C.  Carpenter,  Cornell 
Umv,  Sibley  Jour  of  Eng,  Jan  1905.) 

57.  The  major  portion  of  a  pile  of  sand  or  stone  may  be  in  condition  for 
use  altho  the  surface  is  frozen. 

58.  In  winter,  we  may  reduce  the  areas  of  the  exposed  layers  of 
the  work,  by  placing  the 'bulkheads  closer  together.     A  day's  work  will  then 
run  to  a  greater  elevation,  and  will  necessitate  the  use  of  stronger  forma. 


1108  CONCRETE. 

59.  Mortars,  placed    in  open  air,  are  more  or  less    injured,  by 
drying  instead  of  setting,  when  the  temperature  exceeds  about  65°  to  70  ; 
but  if  mixed  only  in  small  quantities  at  a  time,  and  quickly  laid  in  masonry 
of  dampened  stone,  so  as  to  be  sheltered  from  the  air,  the  injury  is  much 
reduced.     The  sand  and  stone  should  both  be  damp,  not  wet,  in  hot  weather, 
and  a  little  more  water  may  be  used  in  the  cem  paste;  also,  if  possible,  not 
only  the  mortar,  while  being  mixed,  but  the  masonry  also,  should  then  be 
shaded. 

Expansion. 

60.  In    variable    climates,    cast    iron    cylinders,    filled    with 

concrete,  are  frequently  split  horizontally  by  unequal  expansion  and 
contraction.  In  such  structures  it  is  safest  to  consider  the  cylinders  as  mere 
molds  for  the  cone;  and  to  depend  only  upon  the  cone  for  sustaining  the 
load. 

For  expansion  coeffs,  see  Reinforced  Cone,  If  9,  p  1110. 

61.  Cracks  and  joints.     In  abutments  or  culverts  over  60  ft  long, 
divide  the  wall  into  sections  of  about  40  ft,  and  finish  one  section  before  be- 
ginning the  other.     Contraction  will  cause  the  joint  to  open,  and  irregular 
cracks  thru  the  body  of  the  wall  will  thus  be  ayoided.     Short  sections  may 
be  completed  without  stopping,  and  horizontal  joints  thus  avoided.     "Very 
small  cracks,  which,  in  stone  masonry,  would  be  difficult  to  find,  show  up 
very  plainly  in  cone."     (W.  A.  Rogers,  R  R  Gaz,  '00/July  6,  p  461.) 

62.  Effect  of  high  temperatures.     During  calcination  of  the  ma- 
terials for  Portland  cem,  the  chemically  combined  water  is  driven  off.    When, 
in  mixing,  this  water  is  returned  to  the  material,  hardening  takes  place;  but 
the  re-application  of  temperatures,  sufficiently  high  to  drive  off  the  water 
again,  reverses  the  hardening  process  and  disintegrates  the  material. 

Chemical  Effects. 

63.  **  Dehydration  of  the  water  of  crystallization  of  cone  probably 
begins  at  about  500°  F  and  is  completed  at  about  900°  F";  but  this  cools 
surrounding  masses,  and  thus  increases  the  heat  resistance  of  the  cone.    J.  C.* 

64.  Rehydration.     Briquets,  kept,  for  6  to  8  hours,  at  1000°  to  1200° 
F  (not  in  contact  with  flame)  and  allowed  to  cool,  showed  practically  no 
strgth;  but  28  days  immersion  in  water  restored   their  strgth  to  that   of 
unheated  briquets. 

65.  Fire  resistance.    In  quartz  sand  the  expansion  coeff  is  twice  that 
of  feldspar;  and  the  expansion,  in  one  direction,  is  twice  tha-t  in  the  direction 
perp  to  it. 

66.  At  the  Baltimore  fire  the  cone,  exposed  to  flames,  was  seldom  dam- 
aged to  a  greater  depth  than  H  inch,  altho  projecting  corners  were  at  some 
places  rounded  off  by  flames  to  a  radius  of  about  2  inches. 

67.  Sea  water  has  apparently  but  little  effect  upon  cone  so  proportioned 
as  to  secure  maximum  density,  and  thoroly  mixt.     Damage  by  sea  water, 
reported  as  taking  place  at  the  water  line,  has  probably  been  due,  in  part,  to 
freezing.     J.  C.* 

68.  Destructiy  action  upon  cone  by  electrolysis  appears  to  be  due  to 
abnormal  conditions  seldom  occurring  in  practice.     J.  C. 

69.  Green  cone  is  injured  by  acids ;  but  first  class  cone,  thoroly  harden- 
ed, is  appreciably  affected  only  by  strong  acids  which  seriously  injure  other 
materials.     J.  C. 

70.  In  the  reclamation  of  arid  land,  where  the  soil  is  heavily  charged  with 
alkaline  salts,  cone,  stone,  brick,  iron  and  other  materials  are  injured 
under  certain  conditions,  at  ground  water  level.     Such  action  can  be  pre- 
vented by  the  use  of  an  insulating  coating.     J.  C. 

71.  Cone  properly  made,  and  having  its  surface  carefully  finished  and 
hardened,  resists  the  action  of  petroleum  and  ordinary  engine  oils.     Oila 
containing  fat  acids  appear  to  injure  cone.     J.  C. 

72.  Sulphurous  and  sulphuric  acid  g'ases,  combined  with  moisture,  cor- 
rode cone,  especially  if  heated 

*  J.  C.    Report  of  Joint  Comm,  A  S  C  E,  A  S  T  M,  Am  Ry  Eng  &  M  \V 
Assn,  and  Assn  of  Am  Port  Cem  Mfrs,  '09,  Jan. 


TESTS.  1109 

Tests  of  Concrete  in  place. 

73.  Tests  of  concrete  in  place  may  be  made  by  analysis  of  a  core 
of  cone,  obtained  with  a  core  drill,*  using  chilled  steel  shot  for  cutting. 
The  bore  holes  are  afterward  grouted.f 

74.  The  ratio  of  cement    to  sand,  in   the  mortar,  is  found   by 
means  of   the  amounts  remaining  undissolved  in  hydrochloric  acid;  sand 
and  cem,  of  the  kinds  used,  and  mortar,  taken  from  the  core,  being  tested 
separately  in  this  way.     (Prof.  R.  L.  Wales,  in  E  N,  '08 /Jan  9,  p  46.) 

75.  The  ratio  of  mortar  to  stone,  in  the  cone,  is  found  (1)  by 
actual  separation  and  by  weighing  the  stone  and  the  mortar  separately,  or 
(2)  by  ascertaining  separately,  and  comparing,  the  specific  gravities  of  the 
stone,  the  mortar,  and  the  cone. 

*  Made  by  Cyclone  Drill  Co.,  Orrville,  O.,  including  small  drills,  worked 
by  hand. 
"  f  B.  G.  Cope,  in  E  N,   '08/Jan/9,  p  41. 


1110  CONCRETE. 

REINFORCED    CONCRETE. 

1.  The  tensile  and  shearing  strengths  of  cone  are  low  as  compared  with 
its  comp  strgth.     Hence  metal  rods  or  shapes  are  embedded  in  cone  struc- 
tures in  those  portions  subject  to  tensile  and  shearing  stresses,  and  in  such 
positions  as  to  take  those  stresses. 

2.  Uses.     Reinfmt  is  used  chiefly  in  the  tension-sustaining  portions  of 
beams  and  girders,  (including  floor-slabs),  cols,  walls,  retaining  walls,  dams, 
etc;  but  it  is  useful  also  in  many  other  cases;  as  for  preventing  hair  cracks 
in  surfaces,  for  which  purpose  a  light  web  of  metal  (wire  mesh,  expanded 
metal,  etc)  is  placed  a  few  inches  back  from  the  face;  for  preventing  fracture 
due  to  unavoidable  sudden  changes  in  cross-section;  for  joining  walls  meet- 
ing at  an  angle  and  liable  to  settle  away  from  each  other;  and  in  culverts, 
enabling  them  to  withstand  hpr  tension  due  to  the  outward  pressure  of  the 
embankment.     For  this  purpose  old  chains  may  be  used,  or  light  rails,  with 
bolts  driven  thru  the  bolt-holes,  to  increase  adhesion. 

3.  Safety.    Modern  reinfd  cone  buildings  are  practically  monolithic,  and 
therefore  more  rigid  than  skeleton  steel  construction. 

4.  On  the  other  hand,  in  the  steel  building,  the  details  are  more  accurately 
worked  out,  and  the  work  is  usually  erected  by  skilled  men,  often  employed 
by  the  steel  mfrs;  so  that  there  is  but  little  chance  of  damage  to  the  material 
in  erection;  whereas,  in  reinfd  cone  work,  the  best  material  may  be  injured 
in  the  using,  and  the  work  thus  rendered  unsafe. 

5.  Good  cone  protects  imbedded  steel  from  corrosion,  both  above  and 
below  fresh  or  sea  water  level;   but  water  may  penetrate  porous  cone  and 
corrode  the  metal.     Cone  laid  very  dry  is  apt  to  be  porous. 

6.  The  steel,  used  in  reinfg  cone,  has  its  ult  strgth  usually  betw  50,000 
and  70,000  Ibs  per  sq  inch,  and  its  elastic  limit  between  25,000  and  35,000 
Ibs  per  sq  inch,  but  cold  working  may  raise  the  elastic  limit  to  40,000  or 
50,000  Ibs  per  sq  inch.     ' '  Deformed  "  bars  are  often  rolled  of  steel  with  much 
higher  elastic  limit  (50,000  to  65,000  Ibs  per  sq  in  claimed)  for  the  sake  of 
economy  of  steel;   but   see  Bar  Reinforcement,  pp  1128,  etc.     As  in  rolled 
iron  and  steel  in  general,  the  elastic  modulus  may  be  taken  as  averaging 
approximately  30,000,000  Ibs  per  sq  inch.     See  U  11. 

7.  Concrete.     In  general  the  necessity  of  working  the  cone  around  the 
reinfg  bars  requires  that  the  agg  for  the  cone  in  reinfd  work  shall  be  smaller 
than  would  be  permissible  in  unreinfd  mass  work;  and  the  vital  importance 
of  adhesion  requires  that  all  the  materials  for  the  cone  shall  be  of  the  best, 
and  the  mortar  not  too  lean  or  too  dry. 

Expansion,  Contraction,  Etc. 

8.  The  shrinkage  of  cone,  while  setting  in  air,  produces  comp  stress 
in  the  reinfmt  and  tensile  stress  in  the  cone  itself.     Setting  under  water,  the 
expansion  of  the  cone  produces  the  opposite  effects. 

9.  The  linear  expansion  coefficient,  a,  of  a  material,  is  that  fraction 
of  its  original  length  which  a  bar  of  it  gains  or  loses  for  each  degree  of  change 
in  its  temp.     Approximately:  Per  degree, 

Centigrade  Fahrenheit 

Insteel 10,000  a   =  0.117  0.065 

In  concrete 10,000  a   =  0.108  0.060* 

10.  The  large  number  of  reinfd  cone  structures  which  have  been  exposed, 
for  years,  to  wide  extremes  of  temp,  without  injury  thru  difference  in  ex- 
pansion, confirms  the  results  of  experiments,  quoted  above,  as  indicating 
thaf  the  diff,  betw  the  expansion  coefficients  of  the  two  materials,  is  negli- 
gible. 

Elastic  Modulus. 

11.  The  elastic  modulus,  Es,  of  rolled  iron  and  steel,  of  all 

kinds  (p  460,)  is  remarkably  uniform  and  constant,  ranging  ordinarily  betw 
27  and  31  (av,  say  30)  millions  of  Ibs  per  sq  inch  =  approx  1.9  to  2.2  (av, 
say  2.1 )  millions  of  kgs  per  sq  cm. 

*W  D.  Pence,  1:2:4  cone,  Jour  Westn  Soc  of  Engrs,  1901,  Vol.  6, 
p  549,  10.000  a  =  0.055  Fahr,  results  nearly  uniform.  Columbia  Univ, 
1:3:6  cone,  10,000  a  =  about  0.065  Fahr. 


REINFORCED   CONCRETE.  1111 

12.  On  the  contrary,  the  clastic  modulus,  EC,  of  concrete  varies 

widely,  not  only  as  betw  diff  mixtures  differently  manipulated,  and  betw  diff 
specimens  made  under  like  conditions  from  like  materials,  but  in  one  and 
the  same  specimen  under  diff  intensities  of  loading;  so  that,  in  stating  the 
results  of  expts,  it  is  usual  to  specify  the  range  of  unit  stress  within  which  the 
observations  were  made. 

13.  In  stone  concrete,  EC  ranges  from  1.5  to  4  (av,  say  3)  million 
Ibs  per  sq  inch,  =  0.1  to  0.28  (av,  say  0.21)  million  kgs  per  sq  cm.     See 
Expt  81  a,  p  1172.     In  cinder  cone,  EC  is    ordinarily  from  20    to    50  % 
less  than  in  stone  cone.     See  If  30,  p  1106. 

14.  The  ratio,  11  (sometimes  called  r  and  R),  =  Es/Ec,betw  the  elas- 
tic moduli  of  steel  and  of  cone  respectively,  is  usually  taken  betw  10  and 
15  for  stone  cone,  with  higher  values  for  cinder  cone.     See  Specifications, 
If  107,  p  1195.     Owing  to  the  variability  of  EC  (see  If  12),  it  cannot  be  a- 
constant  quantity,  even  during  the  range  of  a  single  experiment  carried 
from  zero  load  to  rupture. 

15.  The  ratio,  n,  is,  however,  of  constant  and  important  use  in  all  cal- 
culations respecting  the  mutual  behavior  of  cone  and  steel. 

16.  Considered  experiments   (Expt  16  a,  p  1146)   seemed  to  show  that 
cone,  when  reinfd  (being  constrained,  by  its  adhesion  to  the  steel,  to  share  in 
its  movemts),  actually  underwent,  without  fracture,  far  greater  elonga- 
tions than  were  possible  in  unreinfd  cone;  but  later  expts  (36,  38,  81  e,  81  f ), 
in  which  the  cone  surface  was  more  closely  observed,  have  indicated  that 
the  supposed  elongation  of  the  cone  was  in  fact  due  to  the  formation  of 
cracks  which  had    before  escaped  observation.     If  the  adhesion,  betw  the 
cone  and  the  steel,  is  uniform,  the  cracking  must  be  evenly  distributed  over 
the  area  of  contact,  and  the  cracks  must  therefore  be  very  numerous  and  very 
fine,  probably  so  fine  as  not  to  endanger  the  materials  thru  the  percolation 
of  water. 

Adhesion.     See  U  58,  p  1126. 

17.  With  rich  and  wet  mixtures,  such  as  are  used  in  reinfd  con- 
struction, the  cem  adheres  very  closely  to  the  steel. 

18.  After  the  adhesion  proper  has  been  overcome,  the  removal  of  the 
steel  from  the  cone  is  still  opposed  by  friction  betw  the  two. 

19.  Upon  the  ability  of  this  adhesion  and  friction  to  resist  the  forces  tend- 
ing to  overcome  them,  depends  of  course  the  safety  of  the  structure. 

20.  Both  adhesion  and  friction,  and  particularly  the  friction,  are  greatly 
affected  by  the  character  of  the  cone  and  by  its  behavior  under  stress  and 
under  temp  changes,  by  the  method  of  testing,  etc. 

21.  In  direct  tests  for    adhesion,  whether    the  steel    is    pulled  or 
pushed,  the  cone  is  always  under  comp,  which  causes  some  lateral  expan- 
sion of  the  cone,  and  therefore  increased  pressure  upon  the  reimfmt.    Hence, 
the  adhesion  may  be  found  higher  than  (other  things  equal)  in  beams,  where 
this  condition  does  not  obtain. 

22.  On  the  other  hand,  where  the  hor  reinfg  bars,  in  a  beam,  are  bent 
upward,  near  the  ends,  and  pass  up  into  the  region  of  compression  and  (as  is 
often  the  case)  to  a  point  over  the  support,  the  high  pressures  upon  the  bar, 
in  those  portions,  may  give  it  greater  adhesion,  as  a  whole,  than  could  be  the 
case  with  a  straight  bar  under  direct  test. 

23.  With  great  lengths  of  imbedment,  the  stretch,  in  the  steel, 
under  high  tensile  stresses,  may  be  such  as  to  contract  the  steel  laterally, 
sufficiently  to  reduce  adhesion.     Hence,  tests  where  the  steel  is  pushed  into 
the  cone,  show  higher  adhesions. 

24.  Ultimate    adhesion.     In    general,  expts    (see   Expts  64  a,  b) 
give,  as  the  ultimate  adhesion  of  good  cone  to  plain  round  rods,  from  200 
to  300  Ibs  per  sq  inch  of  contact  surface.     With  smooth  round  rods,  in  a 
beam,  Kleinlogel  (Beton  und  Eisen,  1904,  pp  227  et  seq)  obtained  560  Ibs 
per  sq  inch.     The  conditions  of  practice  generally  differ  greatly  from  those 
obtaining  in  the  laboratory. 

25.  Working  bond  stress.    In  beams  subject  to  shock,  about  50  Ibs 
per  sq  inch;  for  quiet  loading,  about  double  this  is  sometimes  allowed.     See 
Specifications,  HH  113-115. 


1112  CONCRETE. 

REINFORCED  CONCRETE  COLUMN'S. 

1.  A  concrete  column  usually  has  longitudinal  steel  rods  embedded, 
near  the  circumference,  thruout  its  length.  If  there  is  no  deflection,  and  no 
slip  between  the  concrete  and  the  steel,  the  two  materials  must  shorten 
equally  under  load.  Hence  (p.  458,  Eq  (3)  )  if  L  =  original  length,  /  = 
change  of  length,  ag  and  ac  =  cross  section  areas;  ss  andsc  =  unit  stresses, 
Eg  and  EC  =  elastic  moduli,  of  steel  and  of  cone,  respectively;  we  have 

8S  =  Es  l/L;  8(.  =  Ee  l/L;  ........................................................  (1) 

and,  since  l/L  is  necessarily  the  same  for  both  materials, 

V*c  =  Et/Ec  =  n>      ss  =  sc  n'<  ......................................................  (2) 

and 

total  stress  in  steel  =  ag  ss   =  ag  s   n  ....................................  (3) 

"    cone  =  ac  s   ....................................................  (4) 


(6) 


c  -c          s       ..................................... 

2.  Example.  A  square  cone  col  16  ins  X  16  ins,  12  ft  long  has,  em- 
bedded in  each  corner,  a  round  steel  rod  1  inch  diam;  cross  section  area  of 
each  rod  =  0.785  sq  inch.  Permissible  unit  comp  stress,  sc  ,  on  concrete,  = 
500  Ibs  per  sq  inch.  Required  the  load  which  may  be  carried  by  the  col.  Here 

Area,  as,  of  steel  =  4  X  0.785  =  3.14  sq  ins; 

Area,  ac,  of  cone  =  16  X  16  —  3.14  =  253  sq  ins; 

Es  =  30,000,000  Ibs  per  sq  inch; 

Ec  =     2,500,000  Ibs    "     "       "   ; 

n     =  ES/EC  =  12; 

Total  stress  taken  by  cone  =  ac  sc  =  253  X  500  =  126,500  Ibs 

"  steel  =  as  sc  n  =  3.14  X  500  X  12  =  18,840  Ibs 

"    column  ....................................................  145,340  Ibs 

f     3.  Here  the  steel  takes  100  X  18,840  -*•  145,340  =  about  13  %  of  the 
entire  load,  a  safe  proportion.     This  proportion  should  not  exceed  20  %,  or, 
i  at  most  30  %. 

4.  A  convenient  rule  is  to  count  each  sq  inch  of  steel,  in  cols,  as 
worth  n  sq  ins  of  concrete. 

5.  Conservative  designers  load  cone  cols  approximately  as  follows: 

Mixture 

Length  1  :  1.5:3         1:2:4         1  :  2.5  :  5  1:3:6 

diam  p  =   P/a   =    Load,  in  Ibs  per  sq  inch. 

<  12  ......................................  600  500  350  350 

12  to  18  ...............................  550  450  300  300 

6.  Longitudinal  reinfg  rods  or  bars  are  usually  placed  symmet- 
rically near  the  outside  of  the  cone,  and  are  covered  by  from  1%  to  2  inches  of 
cone.     The  rods  should  be  tied  together,  by  smaller  rods  or  by  wires,  at  in- 
tervals not  exceeding  the  diam  of  the  col. 

7.  Specifications  usually  require  that  the  aggregrate  cross-section  area 
of  compression   rods  shall   not   exceed    from  2  to  3  %  of  the   cross- 
section  area  of  the  col. 

8.  In  buildings  of  say  three  or  four  stories,  the  rods  of  each  sec- 
tion are  bent  in,  near  their  tops,  to  form  a  cylinder,  18  or  20  ins 
high,  of  smaller  diam  than  the  main  cyl  below;  and  the  section  next  above 
fits  down  over  this  portion,  so  that  the  two  sections  overlap  the  length  of 
the  reduced  portion. 

9.  Owing  to  their  much  greater  cross-section  areas,  and  to  the  lower  unit 
stresses  in  their  materials,  reinfd  cone  cols  are  much  less  liable  to  failure  by 
deflection  than  are  steel  cols. 


REINFORCED   COLUMNS.  1113 

10.  For  ultimate  loads  on  longitudinally  reinforced  con- 
crete columns  liable  to  deflection,  we  have  the  Rankine  formula: 

»-T-  -r+irsi™  (8) 

where 

P   =  ult  total  load  on  col; 

a    =  cross  section  area  of  col; 

p    =  P  /a  =  ult  unit  load  on  col; 

8     =  ult  comp  unit  strgth  of  cone  cubes; 

K  =  L/r  =  length/least  radius  of  gyration; 

Prof.  Morsch  gives  m   =  0.0001.     Eisenbetonbau,  '08,  p  73. 

Hooped  Columns. 

11.  Columns  reinforced  with  hoops  (or  spirals)  of  steel,  or  with 
web  reinforcement  bent  into  cylindrical  form,  show  high  ult  strgths  and  are 
largely  used;  but  they  undergo  considerable  deformation  before  the  strgth 
of  the  hoops  is  developed;  the  hoops  acting  much  like  a  steel  cylinder, 
filled  with  sand,  such  cylinders  being  unable  to  act  until  the  sand  is  com- 
pressed. 

12.  Expts  at  Watertown  (Tests  of  Metals,  1905)  show  that,  when  the  col 
is  subjected  to  loads  of  from  100  to  1000  Ibs  per  sq  inch,  the  unit  lateral  de- 
formation is  less  than  one-fourth  the  unit  longitudinal  deformation.     Thus, 
if  the  col  shortened  0.0004  of  its  length,  its  diam  increased  less  than  0.0001  of 
its  original  dimension. 

13.  From  tests  at  the  Univ  of  Illinois  (Am  Soc  Testg  Matls,  Procs,  1907, 
p  382)  Prof.  A.  N.  Talbot  derives  the  following  formulas  for  the  ult  strgths  of 
hooped  cylindrical  cone  cols,  1:2:4,  wet  mixture;  av  age,  60  days;  cols 
12  ins  diam,  10  ft  long.     Covering,  over  the    hoops,  generally  <    %  inch. 
Hoops,  1  inch  wide,  gage  Nos  8,  12,  16,  electrically  welded,  spaced  generally 
2  ins  c.  to  c.     Let 

p        =  ult  strgth  of  col,  Ibs  per  sq  inch; 
c         =  ratio  of  hooping  to  cone  core; 
1600  =  comp  strgth  of  cone,  Ibs  per  sq  inch. 
Then, 

For  mild  steel,       p   =   1600   +     65,000  c  ; (9) 

"  higher    "  p    =    1600   +    100,000  c  ...' (10) 

1-4.  Assuming  that  the  ult  unit  stress,  in  tongitudinal  col  reinfmt,  is  25 
times  that  in  the  cone,  the  hooping  gave  additional  ult  strgth  from  2  to  4 
times  that  given  by  longitudinal  reinfmt. 

15.  M.  Considered  expts  (Genie  Civil,  Nov  1902),  with  spirally  reinforcedN 
cone  cols,  indicate  that  the  bars,  forming  the  hoops,  should  have  a  diam  of  ap-  \ 
proximately  1/40  of  the  diam  of  the  col;  that  the  pitch  of  the  spirals  (dis-  I 
tance  between  hoops)  should  be  from  K  to  %  the  diam  of  the  col;  and  I 
that  the  steel,  in  the  hoops  or  spirals,  adds,  to  the  ult  resistance  of  the  col,  I 
2.4  times  as  much  as  the  same  weight  of  metal  used  as  longitudinal  reinfg.  I 
He  gives  the  formula 

Ultimate  total  load  on  col  =  1.5acc  +  se  (a  +  2.4  A) (11) 

where 

ac  =  cross  section  area  of  col  inside  of  spiral; 
c     =  ult  comp  unit  strgth  of  plain  cone  in  short  blocks; 
se  =  elastic  limit  of  steel; 

a    =  cross  section  area  of  existing  longitudinal  reinfmt; 
A  =  "  longitudinal  reinfmt  of  equal  wt  with  the 

spiral. 


1114 


CONCRETE. 


*  olinuii   Footings. 

16.  In  a  column   footing,  the  stresses  are  analogous  to  those  in  a 
floor  slab  resting  upon  a  col;  but,  owing  to  the  relatively  limited  spread  of 
the  footing,   the  moments  and  shears   are  heavy,   requiring  considerable 
depth.     The  heaviest  stresses  are  under  the  edges  of  the  col.     Hor  rods,  in 
the  footing,  are  analogous  to  rods  near  the  top  of  a  beam,  over  the  support; 
i.e.,  they  take  negative  moms,  and  some  of  them  should  be  bent  upward, 
or  provided  with  stirrups,  just  beyond  the  edges  of  the  col. 

17.  Figs  1  and  2  (T  &  M,  pp  261,  262).     Fig  1:    Two  series  of  main 
reinfg  rods,  a  a',  b  b',  crossing  at  right  angles  under  the  col,  with  diag  rods, 


JL 


a' 


(a) 


1.     Column  Footing. 


<J   !  i  i   '  ,1 

^cSc  !   !   i  I   L>*^*-^" 


oo  (&) 

Fig  2.     Column  Footing. 

d  d',  d'd'.     Fig  2:  Combined  beam  and  slab.     Side  wings  of  slab  tend  to 
bend  upward,  breaking  away  from  the  beam  at  C  and  C. 


REINFORCED    BEAMS. 


1115 


REINFORCED  CONCRETE  BEAMS. 

1.  Cone  is  ordinarily  from  eight  to  ten  times  as  strong  in  comp  as  in  ten- 
sion.    Hence,  in  an  unreinforced  cone  beam  of  rectangular  section,  under 
bending  stresses,  failure  occurs  on  the  tension  side. 

2.  The  ease  with  which  steel  can  be  embedded  in  cone,  the  practical 
equality  of  the  expansion  coeffs  of  the  two  substances,  the  strong  adhesion 
between  cone  and  steel  and  the  practicability  of  supplementing  this  adhesion 
by  lugs  or  other  lateral  projections  from  the  surface  of  the  steel,  facilitate 
combinations  in  which  the  principal  service  of  the  cone  is  to  resist  comp, 
while  that  of  the  steel  is  to  resist  tension. 

3.  The  method  of  manufacture  of  cone  is  such  that  its  behavior,  in  a  given 
case,  is  less  certain  than  that  of  steel. 

Owing  to  this  and  to  uncertainty,  as  to  the  degree  of  adhesion  betw  cone 
and  steel,  on  which  their  united  action  depends,  the  theory  of  such  beams 
is  at  once  more  complicated  and  less  exact  than  that  of  steel  beams  of  eco- 
nomical sections.  In  the  design  of  reinfd  cone  beams,  proper  allowance  must 
be  made  for  this  fact,  and  extreme  refinement  is  out  of  place. 

General  Theory. 

4.  Simple  reinfd  cone  beam,  of  rectangular  section,  Fig.  1. 


Fig  1.     Reinforced  Concrete  Beam.     Theory. 
Fundamental  assumptions. 

1.  Cross  sections,  plane  before  flexure,  remain  plane  under  flexure. 

2.  Initial  stresses  (from  shrinkage,  etc)  are  neglected. 

3.  No  slipping  occurs  between  cone  and  steel.    Hence  they  deform  equally. 

4.  The  tensile  resistance  of  the  cone  is  neglected. 

5.  The  elastic  moduli,  Es  and  EC,  of  steel  and  of  cone  respectively,  and 
hence  their  ratio,  n  =  ES/EC,  remain  constant. 

5.  Notation.     Referring  to  Fig  1,  let: 

b      =  breadth  of  cross  section  of  beam,  perp  to  the  paper; 

d      =  dist  from  comp  side  of  beam  to  cen  of  grav  of  steel; 

kd    =       "       "          "       "     "       "     "     neutral  axis; 

z       =       "       "          "       "     "  '     resultant  of  comp  forces; 

(1-fc)  d   =       "        "    cen  of  steel  to  neutral  axis; 
df  =  yd  —       "       "      "    "     "      "  resultant  of  comp  forces 
=  leverage  of  resisting  couple ; 

]       =  d'/d; 
ES    =  elastic  modulus  of  steel; 


=  unit  elongation  of  steel; 
=  unit  tensile  stress  in  steel  f; 


=  unit  shortening  of  concrete;* 
=  unit  comp  stress  in  concrete;*! 


*  In  the  outermost'  fibers  on  the  compression  side  of  the  beam. 
t/s  and  fc  are  the  actual  unit  stresses.     See  H  13,  p  1118. 

74 


1116  CONCRETE. 

as     =  cross-section  area  of  steel;        ac    =  bd  =  cross-section  area  of  cone 

above  cen  of  steel; 

T     =  sum  of  tensile  stresses  in  steel  ;  C    =  sum  of  comp  stresses  in  concrete; 
n      =  ES/EC  =  ratio  of  elastic  moduli  of  steel  and  cone; 
p      =  as/ac    —  ratio  of  steel  area  to  that  portion  of  cone  area  which  is 

above  cen  of  steel;* 
Mg  =  resisting  moment,  based  upon  the  max  allowable  value**  of/.  ; 

Mc-       "  "         '  .............  fc; 

M    =  actual  resisting  moment. 
Then  ag  =  p  ac  =  p  b  d. 

Stresses,  Moments,  Design. 

6.  Figs  1  and  2§  and  HU  7  to  20  illustrate  the  relations    existing 
between  the  important  factors,  k,  j,  fs,  fc,  p,  Ms,  Mc  and  M;  when 
neither  f3  nor  fc  exceeds  the  elastic  limit.     When  they  exceed  that  limit,  see 
H«I  21,  22,  p  1122. 

7.  In  equilibrium,  the  bending  moment  of  the  load  (see  p  474)  is 
balanced  by  the  equal  resisting  moment  of  the  couple  composed  of 
the  two  equal  hor  forces,  T  and  C;  these  forces  being  the  resultants  respec- 
tively of  the  tensile  stresses  in  the  steel  and  of  the  compressive  stressest  in 
the  cone. 

8.  The  tensile  stresses,  fg  ,  in  the  steel,  are  assumed  to  be  uniformly 
distributed  over  its  entire  cross  section,  ag;  and  their  resultant,  T,  is  there- 
fore taken  as  acting  at  the  grav  cen  of  the  steel  area;'  but  the  compres- 
sive stresses,  in  the  cone,  in  any  cross  sec,  decrease  uniformly}:  from  a 
max,  fc  ,  at  the  upper  surf  of  the  beam,  to  zero,  at  the  neutral  axis.     Their 
resultant,  (7,  is  therefore  applied  at  a  point  distant  kd/3  below  the  top  of 
the  beam,  kd  being  the  distance  from  top  of  beam  to  neutral  axis,  and  d  the 
distance  from  top  of  beam  to  grav  cen  of  steel. 

9.  Value  of   "J."     The    lever    arm,   d',   of   the    resisting 
couple  is  therefore 

d'  =  jd  =  d  —  kd/3  =  d  (1  —  fc/3)  .............................................  (D 

and  we  have 

,-  =  d'/d  =  1  —  fc/3  ......................................................................  (2) 

For  approx  values  of  /,  see  1  12. 

10.  Value  of  "It."     From  assumption  1,  U  4  we  have 

ec/es  =  fc/(l  —  A;)  ...........................................................................  (3) 

From  assumption  5,  we  have 

fc  =  ecEc->         /.  -  «.*.-  ...............................................................  (4> 

Hence 

**       e*  Ec  =  k  (4a) 

'" 


/,         esEs         l-k'Es        n(l—  *)'" 
For  equilibrium,  C  =  T;  but 

C  =  fcbkd/2  =  ecEcbkd/2  ......................................................  (5) 

and       T  =  fs  as  =  fs  p  b  d  =  eg  ES  p  bd  ........................................  (6) 

e,  E,  \  —k 

Hence,  k  =  2  p  -^   =  2  p  n  —  —  -  ; 


=    l/(pn)2   +   2pn  —  p  n  .............................  .  ................................  (7) 


*See  tf  15,  16,  p  1118.  **  See  H  13,  p  1118.  . 

t  Below  the  neutral  axis,  the  cone  is  in  tension,  but  its  tensile  stress  is 
neglected.  See  assumption  4,  If  4,  p  1115.  •  J  See  Uf  21,  22. 

§  Figs  2  and  3  are  by  Prof  A.  W.  French,  A  S  C  E-,  Trans,  Vol  56,  '06, 
pp  362,  etc. 


REINFORCED   BEAMS. 


1117 


2.00 


steel  area— cohcrete  area 

n-lQ  for  full  curves 
Ec  I  n  =15     "  dotted  curves 


Steel  lines  plotted  for  n= 
Approximate  for  w= 


0.25  0.50          0.75 

Scale  of  1OO  p 

Fig  2.     For  Working  Stresses.     (For  ultimate  stresses,  see  Fig  3.) 
k    =    l/  (pn)2  +  2  pn  —  pn,         j    =   d'  /  d, 
fm   =   unit  stress  in  steel,  f^,   =   unit  stress  in  cone  at  top  of  beam, 
p    =   asjac   =   ratio  of  steel  area  to  cone  area, 

,]lfc   =   resistg    mom,   based    upon    allowed   value   of   /s,/c,reHp, 
M   =   resistg  mom,  actual. 

; 


n  =  ES/EC  .  Solid  curves  represent  n  =  10;  dotted  curves,  n  =  15 

Steel  lines  plotted  for  n   =    10;  approx  for  n  =    15. 


1118  CONCRETE. 

11.  Hence  the  position    of  the  neutral    axis  (given  by  k)  de- 
pends solely  upon  the  ratio,  p,  of  steel  area  to  cone  area,  and  upon  the 
ratio,  n,  of  elasticity  betw  steel  and  cone.    For  appro x  values  of  k,  see  H  12. 

12.  Approximate  values  of  /  and  k.     See  Fig  2. 

when  and  we  have  and 

n   =   10,  p   =   0.010:      j    =   0.88;         k   =   0.36: 

p   =   0.015:      j   =   0.86;         k   =  0.42; 

n   =    15,  p    =   0.010:       j    =   0.86;          A;    =   0.42; 

p    =   0.015:       j   =   0.84;          /k    =   0.48. 

13.  When,  as  in  reinfd  cone,  two  widely  diff  materials  are  used  in  con- 


junction, it  usually  happens  that,  owing  to  the  impracticability  of  always 
giving,  to  each,  its  ideal  cross-sec  area,  one  or  the  other  is  un- 
avoidably and  uneconomically  subjected  to  less  than  its  maxi- 
mum allowable  stress.  Thus,  with  a  given  value  of  p  =  as/ac , 
if  we  load  the  beam  until  either  fg  or  fc  reaches  its  max  allowable  limit,  the 
other  (fc  or  fg  respectively)  will  usually  remain  below  its  max  allowable 
limit.  See  If  19  /.  Let  FS  and  FC  =  respectively  the  max  allowable 
values  of  t'm  and  l'c. 

14.  Moments.     For  resistg  moms,  based  upon  the  max  allowable  values, 
Fg  and  FC  ,  of  fg  and  fc  respectively,  we  have: 

Mg  =  Td'  =  Fsasj  d  =  Fgpjbd* (8) 

Mc  =  C  d'  =  C  j  d  =  Fc  b  k  d  j  d/2  =  FC  k  j  b  d  2/2 (9) 

For  usual  values,  we  may  take  (see  H  12):  j  -  %;  k  =  %, 
k  j  =  yz.  Hence,  approx, 

Ms  =   7  Fg  agd/8; 
Mc  =   Fc  b  d  V6. 

But  the  actual  resisting;  mom.  M,  of  the  sec,  in  any  given  case, 
can  of  course  have  but  one  value;  and  this  is  the  less  of  the  two  values, 
M s  and  M  .  Since  j  b  d  2  is  common  to  both  these  values,  M  is  determined 
by  whether  Fg  p  or  FC  k/2  is  the  greater. 

15.  Relation  between  fs ,  fc  and  p.     Since  C  =  T,orfcbk  d/2 
«=  fs  p  b  d,  we  have: 

'•=!!•       '«  --''':      "  -  "27, (10> 

From  Eq  (4a)  we  have: 

Hence  k 
andp   =   */,/2/.  =   — -J^L_  --  f    ,    ™        x   (11) 

i( 

Usually,  p  ranges  from  0.010   to  0.015.     It  is    seldom  <  0.005  or 

16.  Note  that  fg  ,  fc  and  p  cannot  be  arbitrarily  selected.     Given  any  two 
of  them,  the  third  depends  upon  the  two  so  given. 

17.  Value  of  M/bd  2.    Let  Fg  and  FC  be  the  max  allowable  values  of 
the  unit  stresses,  fg  and  fc ,  in  steel  and  in  cone  respectively.     Then,  from 
eqs  (8)  and  (9),  II  14,  we  have  (Fig  2,  lower  portion): 

Mg/bd2  =  Fspj   =   Fgp(l  —  fc/3); 

(nearly  straight  lines,  for  steel) (12) 

Mc/bd2  =  Fc  k  j/2   =   Fc  k  (1  —  fe/3)/2; 

(curved  lines,  for  cone) (13) 


REINFORCED    BEAMS.  1119 

The  dotted  and  solid  curved  lines,  for  cone,  represent  n  =  15  and  n  =  10, 
respectively.  The  nearly  straight  lines,  for  steel,  are  plotted  for  n  =  10, 
but  are  sufficiently  approx  also  for  n  =  15. 

18.  The  upper  portion  of  Fig  2  gives  values  of 


k  =  y  2  p  n  +  (p  n)*  —  p  n, 
(see  f  10)  and  of 

j    =   1  —  fc/3   =  d'/d, 

corresponding  to  given  values  of  p,  for  n  =  10  and  n  =  15.  Note  that  j 
varies  but  slightly  with  p. 

Examples. 
I.    Investigation. 

Required  the  resisting  moments*  Ms  ,  MC  and  M. 
19  a.  Given    a    rectangular    reinfd    cone    beam:     6  =  8*; 

d  =  20";  ac  =  bd  =  8  X  20  =  160  sq  ins;  n  =  Et/Ec  =  15.  Let  Fg 
=  16,000,  and  FC  =  500  Ibs  per  sq  inch,  be  the  max  allowable  values  of  the 
unit  stresses,  fs  and  fc,  in  steel  and  in  cone  respectively;  and  let  P  be  the 
value  of  p  based  upon  these  max  allowable  stresses. 

F8 
Then  F8/FC  =  32;    ^r     +   1    =   3.133;   and,  from  Eq  (11),  U  15,  we 

have: 

P   t   32->rll33    -   °-°04987' 

as  given  by  the  intersection,  in  Fig  2,  of  radial  line,  for  fg  =  16,000,  with 
dotted  curve  for  fc  =  500. 

19  b.  (Case  1)  Reinforced  with    two    round   rods,  %"  diam; 

as     =>  2  .  JT  0.375  2   =   0.884  sq  ins; 

p      =  ag/ac  =  0.884/160   =   0.005525  >  P; 

pn    =  15  X  0.0055   =  0.0825; 

k      =    l/(jm)2  +  2  pn  —  pn 


+  0.1650  —  0.0825   =   0.3322; 
d'     =  d  j   =  d  (1  —  fc/3)   =   20  (1  —  0.1107)   =   20  X  0.89  =  17.8  ins; 
C     =  Fc  b  k  d/2   =   500  X  8  X  0.3322  X  10   =   13,288  Ibs; 
Mc  =  Cd'     =   13,288  X  17.8   =   236,526  inch-lbs; 
T     =  F9  as   =   16,000  X  0.884   =   14,144  Ibs; 
Mg  =  Td'     =   14,144  X  17.8   =  251,763  inch-lbs; 
M    =  Mc  =  236,526     "     "    . 

Notice  that  where,  as  in  this  case  and  in  Case"  2,  P  <  jp,  the  mom, 
Mc  ,  based  upon  the  max  allowable  stress,  F  c  in  the  cone,  is  the  actual 
mom,  M.  Where  P  >  p,  MS  is  the  actual  mom. 

19  c.  By  Fig  2.  The  intersection  of  the  vert  line,  on  100  p  =  0.55, 
with  radial  line  for  fg  =  16,000  Ibs  per  sq  inch,  gives  M  s/bd2  =  78.7;  and 
M,  =  78.7  6  rf2  =  78.7  X  8  X  202  =  251,840  inch-lbs;  but  the  intersection 
of  vert  line  on  100  p  =  0.55,  with  dotted  curve  (n  =  15)  for  fc  =  500  Ibs 
per  sq  inch,  gives  Mc/bd2  =  74;  and  M  =  MC  =  74  bd-  =  74  X  8  X  20» 
=  236,800  inch-lbs. 


1120  CONCRETE. 

19  d.  (Case  2)  Reinforced  with  3  round  rods,  1"  diam; 

as     =  37T0.52   =   2.356  sq  ins; 

p      =  as/ac   =   2.356/160   =   0.01473  >  P; 

pn   =  15  X  0.01473    =  0.2209; 

k      =    i/  Tpn)2  +  2  pn  —  pn 

.=  I/  0.22  2  +  0.44  —  0.22   =   0.48; 

df     =  rf/   =  d  (1  —  Jfc/3)    =   20  (1  —  0.16)    =   20  X  0.84    -   16.8; 
C     •=  Febkd/2   =   500  X  8  X  0.48  X  10   =   19,200  Iba; 
jjfc  =  Cd'     =    19,200  X  16.8      =   322,560  inch-lbs; 
T     =  Fsas   =   16,000  X  2.356   =   37,696  Ibs; 
Ms  =  Td'      =  37,696  X  16.8     =   633,293  inch-lbs; 
M    =  Mc       =  322,560     "       "  . 

19  e.  By  Fig  2.  The  intersection  of  the  vert  line  on  100  p  =  1.473, 
•with  radial  line  for/g  =  16,000  Ibs  per  sq  inch,  would  give  (on  a  sufficiently 
accurate  diagram)  M,/bd  2  =  198;  and  MS  =  198  6  d2  =  198  X  8  X  20  2  = 
633,600  inch-lbs;  but  the  intersection  of  vert  line  on  100  p  =  1.473,  with 
dotted  curve  (n  =  15)  for  fc  =  500  Ibs  per  sq  inch,  gives  Mc/bd2  =  101; 
and  M  =  MC  =  101  6  d2  =  101  X  8  X  20  2  =  323,200  inch-lbs. 

19  f.  It  will  be  noticed  that/in  these  cases,  an  increase  of  166.5  %, 
in  the  amt  of  steel,  has  increased  the  resisting-  mom  (which  still 

depends  upon  the  cone)  by  less  than  38  %;  and  the  steel,  in  Case  2,  is 
stressed  to  only  about  8,000  Ibs  per  sq  inch  or  half  the  max  allowable  stress 
(intersection  of  vert  for  100  p  =  1.473,  with  dotted  curve  f  or  /  =  500,  is 
nearly  intersected  by  radial  line  for  fs  =  8,000).  See  U  13. 

19  g.     In  both  cases,  (1)  and  (2),  the  intersection  of  radial  line  for  fs  = 
Fs=  16,000,  with  dotted  curve  for  fc  =  FC  =  500,  would  give  (on  a  sum- 
ciently  accurate  diagram)  p  =  P  =  0.004987;  M/bd*  =  71.5,    and  M  = 
71.5  bd2  =  228,800  inch-lbs,  the  actual  mom,  for  the  given  b  and  d,  in  the 
ideal  case  where  fs  and  fc  =  respectively  FS  and  FC  =  16,000  and  500. 

II.    Design. 

20  a.    Conversely,    given    the    bending*    moment,    230,500 
inch-lbs;  F3  =  16,000;  Fc  =  500  Ibs  per  sq  inch;  whence  P  =  0.004987, 
as  before.     Required  b  and  d. 

Let  K  and  J  =  the  values  of  k  and  of  j  respectively,  corresponding  to 


Here  we  have 

Pn  =  15  X  0.004987   =   0.075; 


K     =         (Pn)2  +  2Pn  —  Pn 

=  l/0.0752  +  0.150  —  0.075   =   0.3193; 
J      =  1  —  A'/3    =   1  —  0.1064   =   0.8936; 
M  2  M  2  X  236,500 


,. 


FSPJ        Fc  KJ        500  X  0.3193  X  0.8963 

2O  b.  An  infinite    number  of  section    areas,  bd,  giving  the 
same  resisting  moment,  M,  may  be  found  from  bd  2. 

20  c.     Thus,  in  the  example  of  H  20  a,  with  bd2  ==  3315,  we  may  have 
b  d2  d 

6  552  23.5 

8  414  20.3 

10  331  18.2  etc,  etc. 


REINFORCED    BEAMS. 


1121 


0.25 


Scale  of 1OO  jp 
0.75  1.00  1.26 


1.50  1.75  2.00 


0.25  0.50          0.75 

Scale  of  1OO  p 

Fig-  3.     For  Ultimate  Stresses. 


' 


l.CJ 


(For  allowable  stresses,  see  Fig  2.) 
P  n'        *   =  d>  I  d> 


fg  =  unit  stress  in  stoel,   f,.  =   unit  stress  in  cone  at  top  of  beam, 

p  =  «s/«c   =    ratio  <;f  steel  area  to  cone  area, 

C  =  resiatg  mom,  based  upon  max  allowed  value  of  fs  ,  fc  resp, 

M  =  resistg  mom,  actual. 


n  =  -^s/-^c  •  Solid  curves  represent  n  =  10;  dotted  curves,  n  =  15. 
Steel  lines  for  n  =   10;  approx  for  n  =  15. 

C7 


1122 


CONCRETE. 


20  d.  It  can  be  shown  (T  &  M,  pp  175-6)  that,  with  given  M,  given  unit 
stresses,  and  given  unit  prices,  the  cost  .of  a  reinfd  cone  beam,  per  unit  of 
length,  varies  inversely  as  d,  directly  as  V  b,  and  directly  as  $  b/d . 
Hence,  for  a  given  bd,  the  deeper  the  beam,  the  less  is  the  cost;  but  practical 
considerations  (such  as  practical  limits  to  reduction  of  b,  requirements  as 
to  head  room,  etc)  often  limit  the  extent  to  which  this  economy  can  be  carried 
in  practice. 

21.  Within  the  limit  of  allowable  working  stresses,  Fig  2, 
the  stresses  and  deformations,  in  the  several  fibers,  are  taken  (assumption  1, 
H  4)  as  proportional  to  the  dists  of  the  fibers  from  the  neutral  axis,  as  repre- 
sented by  the  shaded  triangle  in  the  small  figure  above  the  diagrams  (said 
triangle  representing  approx  the  lower  portion  of  the  parabolic  area  shown 
in  Fig  3);  and  we  have,  Eq  (7),  t  10, 

It    =    V  (pn)2  +  2  pn  —  pn. 

22.  For  stresses  exceeding;  the  allowable  workg  stresses, 

up  to  the  ult,  Fig  3,  assumption  1  is  inadmissible,  we  must  employ  the  entire 
parabolic  area,  its  vertex  corresponding  with  the  ult  comp  strgth  of  the 
cone;  and  we  have 


k    =    l/(3pn/2)2  +  3pn  — 3pn/2  (14) 

Fig  3  gives  values  of  j,  k  and  M  /b  d2,  for  ult  values  of  fs  and  ff. 

23.  Note  that,  for  steel  stresses,  fs ,  not  exceeding  the  usual  elastic  limit, 
and  with  fc  ultimate  <  2000  Ibs  per  sq  inch,  the  ult  resistg  mom  in- 
creases directly  with  the  amount  of  rciiifmt  tintil  this  reaches 
2  %  or  over.  Thus,  Fig  3,  with  fs  =  30,000  Ibs  per  sq  inch,  fc  ult  <  2000, 
and  p  =  0  to  2  %,  we  have  M  /bd  ~  =  approx  25,000  p. 
Tee  Sections. 

2-1.  Tee  sections.  Fig  4.  b  =  flange  width;  6'  =  stem  width;  I  = 
flange  thickness;  d  =  depth  from  top  of  flange  to  cen  of  steel;  k  d  = 
depth  of  neut  axis;  df  —  j  d  =  leverage  of  T  and  (7. 


X-6-K 
i       i 

Fig  4.     Reinforced  Tee  Section.     Theory. 

25.  When  the  tops  of  rectangular  beams  are  connected  by  slabs,  the 
whole  being  placed  at  one  time  and  properly  bonded,  all  or  a  part  of  the 
slab  may  be  considered  as  a  compression  flange,  in  some  respects 
similar  to  those,  composed  of  angles  and  plates,  of  steel  plate  girders. 

26.  The  width  of  slab.  6,  Fig  4,  which  acts  as  flange,  is  sometimes 
taken  as  the  distance  between  beams,  but  should  not  exceed  %  of  the  span 
of  the  beams.     See  Specifications,  Ht  168-170. 

27.  Exact  analysis  of  such  a  section  is  hardly  possible,  but  it  is  believed 
that  the  following  method  is  reasonable  and  safe. 

28.  Determine  the  ratio,  p  =  «g/ac,  of  steel  area  to  cone  area  as  tho  the 
beam  were  rectangular,  with  depth  =  d,  and  width  =  the  flange  width.  6. 
With  this  value  of  p,  determine  the  position  of  the  neutral  axis.     If  this 
falls  within  the  slab  or  just  at  its  lower  side,  the  resisting  moment  is  found 
exactly  as  with  any  rectangular  section.     See  Case  1,  U  19. 

29.  If  the  neutral  axis  falls  below  the  bottom  of  the  slab,  the 
position  of  the  neutral  axis  will  not  be  exactly  given  by  the  equation  for 
rectangular  beams;  but  the  difference  will  not  be  important. 

30.  The  resisting  moment  is  Cd'  or  Td' ',  whichever  is  the  less. 


REINFORCED   BEAMS.  1123 

31.  Examples. 

(1)  Neutral  axis  within  the  slab. 

Let  6    =  601ns;  b'    =  Sins;  d   =   20  ins;  t   =   5  ins;  max  allow- 
able unit  stresses,  FC   =   500,  FS   =    16,000  Ibs  per  sq  in;  EC   = 
3,000,000;  Es  =   30,000,000;  n  =   10.     Let  there  be  3  round  steel 
rods,  diam   =    1  inch. 
Then 


k  =   V  (pn)2  +  2  p  n  —  p  n 

=  i/Ti"0~X~OT002ya  +  2  X  10  X  0.002  —  10  X  0.002    =   0.18; 
k  d  =  0.18  X  20    =   3.6  ins; 

C  =  Fc  b  k  d/2   =   500  X  60  X  0.18  X  20/2   =   54,000  Ibs; 
T  =  3  X  0.785  Fs    =   say  37,650  Ibs. 

Using  the  smaller  value  (that  for  the  steel)  we  have  : 

M   =    T  d'   =  T  (d  —  d  fc/3)    =  37,650  (20  —  3.6/3)  =  707,000  inch-lbs. 
(2)  Neutral  axis  below  the  slab. 

Letb   =   60  ins;  b'  =   10  ins;  d   =   30  ins;   t   =   4  ins;  Fc,Fs,Ect 
Es  and  n  as  in  Example  (l)r  6  round  steel  rods,  diam  =  1  inch.     Then 

'In5   =   0.0026,  and  k   =   0.2;  k  d  =  0.2  X  30  =  6. 


^     n 

OU   X   oU 

32.  Since  the  comp  unit  stress,  in  the  outer  fibers  of  cone,  is  assumed  to 
be  FC  =  500  Ibs  per  sq  inch,  the  stress,  at  the  lower  side  of  the  slab,  is  500 
(k  d  —  t)/k  d  =  500  X  2/6  =  167;  and  the  average  stress,  in  the 
slab,  is  5°°  +  1(£  =  333  Ibs  per  sq  in. 

33.  The  2  inches  of  stem,  which  lie  between  the  neutral  axis  and  the 
lower  side  of  the  slab,  exert  some  comp  resistance,  but  this  is  neglected, 
with  a  small  error  on  the  safe  side. 

34.  The  position  of  the  center  of  gravity  of   the  compressive 
forces  in  the  slab  may  be  found  as  for  a  trapezoid;  but  it  is  usual,  safe,  and 
sufficiently  approximate,  to  assume  that  it  is  at  the  cen  of  the  slab,  or,  in 
this  example,  at  a  distance  of  d  —  t/2  =  30  —  2  =  28  ins  above  the  cen  of 
the  steel.     The  mom  of  these  forces  is  then  MC  =  333  X  60  X  4  X  28    = 
2,238,000  inch-lbs;  but  the  moment  of  the  tensile  resistance  of  the  steel  is 
only  Ms  =  6  X  0.785  X  16,000  X  28  =  2,110,000  inch-lbs;  and  this  mom, 
being  the  less  of  the  two,  is  to  be  taken  as  the  actual  mom,  M. 

Shear. 

35.  Shear.     In  addition  to  the  hor  stresses,  resisted  by  compression  in 
the  cone  and  by  tension  in  the  longitudinal  steel  reinfmt,  the  vertical  shear- 
ing stresses  require  attention  in  relatively  deep  beams  under  heavy  loads. 

36.  For  the  total  shear,  V,  in  any  vert    section,  distant  x  from 
a  support,  we  have  : 

V   =   R—  W  ............................................  (15) 

where        R     =   upward  reaction  at  the  support; 

W   =   the  total  of  any  loads  in  the  distance,  x. 

37.  The  vert  shear  is  sometimes  provided  for  by  using  a  large  safety 
factor  with  the  ult  shearing  strgth  of  cone,  which  is  usually  taken  at  from 
500  to  800  Ibs  per  sq  inch,   while   the  working  shearing  stress  is   often 
restricted  to  from  30  to  50  Ibs  per  sq  inch.     But  see  Stirrups,  U1[  38,  etc. 


1124  CONCRETE. 

Shear  Reinforcement.     Stirrups. 

38.  Shear  Reinforcement.     Where  the  loading  produces  a  shear- 
ing stress  exceeding  the  limit  assumed  for  plain  cone,  the  beam  is  often  reinfd 
by  vert  stirrups,  which  consist  of  rods,  bent  into  the  shape  of  a  letter  U, 
and  passing  under  the  hor  bars  and  up  to  near  the  top  of  the  beam;  or,  in 
the  case  of  Tee  beams  (Fig  4),  into  the  slab. 

39.  The  distance  between  stirrups  is  sometimes  made  such  that, 
within  a  hor  length  =  d',  there  shall  be  an  aggregate  sectional  area  of  vert 
steel  bars  sufficient  to  carry  the  vert  shear  by  means  of  the  permissible  unit 
tension  in  the  steel. 

40.  Example. 

Consider  the  T  beam  of  example  (1)  ^[31,  Fig  4;  V  =  8  ins;  b  =  60  ins; 
d  =  20  ins;  k  =  0.18;  d'  =  20  —  k  d/3  =  20  —  1.2  =  18.8;  safe  mom  of 
resistce,  M  =  707,000  inch-lbs.  Let  span  L  =  20  ft  =  240  ins.  Then,  foi 
a  uniform  load,  we  have  W  =  8  M/L  =  8  X  707,000/240  =  23,600  Ibs. 

Shear  at  ends   =    W/2   =   11,800  Ibs. 

With  safe  unit  shearing  stress  =  50  Ibs  per  sq  inch,  we  have  safe  shear 
resistance  of  plain  cone  in  section  =  50  b'  d'  =  50  X  8  X  18.8  =  7,5T)0  Ibs 

Under  uniform  load,  this  shear  occurs  at  a  dist,  from  the  ends, 
(11,800—  7.500)  L 

2  X  11.800  =  3'65  ft' 

From  this  point  to  the  center  of  the  span,  the  cone  is  able  to  care  for  the 
shear,  and  no  stirrups  are  there  reqd.  But  see  ^\  41,  45. 

Between  this  point  and  each  support,  let  the  stirrups  be  of  %  inch  round 
steel;  aggregate  cross  section  area  of  the  two  limbs  of  each  stirrup  =  0.22 
sq  inch. 

Allowing  16,000  Ibs  per  sq  in,  one  stirrup  will  sustain  16,000  X  0.22  = 
3,520  Ibs. 

The  total  shear,  11,800  Ibs,  at  the  support,  divided  by  3520,  gives  3.3 
as  the  number  of  stirrups  required,  in  18.8  ins  of  length  of  beam; 

or  the  spacing1,  next'to  the  ends,  should  be        '      =  5.5  ins. 

Let  the  load,  W,  =  23,600  Ibs,  be  uniformly  distributed.  Then,  at  a 
point  3  ft  from  the  end,  V  =  ^j1--  X  11,800  =  8260  Ibs;  8260/3520  = 
2.35;  and  stirrup  spacing-  =  18.8/2.35  =  8  ins. 

41.  The  spacing-  may  be  made  to  vary  uniformly  betw  these  limits; 
and  it  would  be  well  for  the  vert  reinft  to  extend  beyond  the  theoretical 
stopping  point  (3.6  ft  from  end;  see  H  40),  by  one  or  two  stirrups  spaced  a 
foot  apart.     See  f  45. 

42.  Let 

A  =  aggregate  vert  cross  sec  area  of  hor  rods,  sq  ins; 
L  =  span,  ft; 

z    =  dist  from  end  of  beam  to  stirrup,  ft; 

S  =  aggregate  cross  section  area  reqd  in  the  2  limbs  of  the 
stirrup,  sq  ins. 

Then,  when  the  stirrups  are  1  ft  apart, 

s_  £(,_*_££!) (16) 

(J.  W.  Schaub,  E  N,  '03/Apr/16,  p  348.) 

43.  In  general,  spacing  betw  stirrups  >  d'. 

44.  The  cone,  in  each  sec,  has  to  act  as  a  connecting  medium  between 
the  hor  and  the  vert  reinft.     It  is  also  subjected  to  comp  forces,  in  transfer- 
ring the  shear  from  one  stirrup  to  the  next.     The  action  here  is  complex, 
and  an  ample  safety  factor  should  be  used. 

45.  In  order  to  provide  against  excessive  loadings,  which  may  come 
temporarily  upon  the  beams  during  construction,  it  is  advisable  to  use 
stirrups,  even  where  not  actually  required  by  the  shearing  stresses  deter- 
mined  theoretically  as   above   for  the  completed   structure  in   use.     The 
etirrups  being  light,  the  cost  of  using  them  is  principally  for  labor;  so  that 
if  any  are  reqd,  it  is  well  to  be  liberal  with  them.     See  U  41. 


REINFORCED   BEAMS. 


1125 


Unit  Shear. 

46.  Unit  shear,  v.  In  any  hor  section  of  a  beam,  Fig  5,  under  uniform 
or  central  loading,  the  hor  tensile  or  comp  stresses  increase  from  the  ends, 
where  they  are  zero,  toward  the  middle  of  the  beam,  where  they  are  a  max. 
Hence,  of  any  two  vert  plane  sees,  1  and  2,  the  section,  2,  nearer  the  cen  of 
the  beam,  will  have  the  greater  hor  stresses,  s. 


: 

. 

V 

c~^i 

Neutral  Axis                    3 

Fr0'  £ 

• 

T 

B 

<?'     ) 

i  L 

^^ji 

Fig  5. 

"1 

Unit  Shear. 

47.  Consider  the  forces  acting  upon  the  rectangular  body,  B,  between  the 
two  sections,  1  and  2. 

48.  At  the  left  section,  1,  the  vert  shear,  V,  coming  from  the  left  support, 
pushes  B  upward;  and  the  tension,  T,  of  the  steel  pulls  B  horizontally  toward 
the  left;  while  the  total  comp,  C,  acting  at  the  cen  of  the  comp  forces,  pushes 
B  toward  the  right. 

49.  At  the  right  sec,  2,  the  vert  shear,  V,  pushes  B  downward;  while  T' 
and  C'  are  in  line  with  T  and  C  respectively,  but  opposite  to  them.     Note 
that  2"  >  T,  and  C'  >  C.     Let  T'  —  T  -  t. 

50.  Let  there  be  no  load  on  B.     Then  V   =   V.*     Since    the    vert 
forces  are  distant  by  x,  their  moment    =    Vx  =  Vx*     The  mom  of  T'  —  T 
is(Tf  —  T)  d'  =  id'.     Hence,  for  equilibrium, 

Vx   =   td';        or    t   =    Vx/d' (17) 

51.  In  a  reinfd  cone  beam,  Fig  5,  we  neglect  the  tensile  strgth  of  the  cone. 
Hence,  the  diff,  7"  —  T  =  t,  of  tension,  between  sees  2  and  1,  must  be  trans- 
mitted, from  the  steel  to  the  neut  axis,  by  a  total  shear,  =  t,  uniform*  in 
each  hor  sec;  and,  since  the  hor  sec  of  the  body,  B,  is  6  x,  we  have,  for  the 
unit  shear: 


v  =  t/bx  =  Vx/d'bx  =  V/bd'  =  V'/bd'*  .... 


•(18) 


Diagonal  Stresses. 

52.  As  a  matter  of  fact,  the  longitudinal  tensile  stresses  and  the  vert  and 
hor  shearing  stresses,  combine  to  form,  and  are  replaced   by,  diagonal 
stresses  ;  and  reinfmt,  against  shear,  is  more  rationally  designed  by  deter- 
mining, as  nearly  as  may  be,  the  directions  and  intensities  of  these  resultant 
diagonal  stresses  (See  t  53),  and  so  placing  the  reinfmt  as  best  to  resist  them. 

53.  From    "Maximum  Unit  Stresses  in  Beams,"  p  494  e,  we  have,  in 
homogeneous  beams,  for  the  angle.  A,  betw  the  neutral  axis  and  the 
resultant  normal  (tensile  and  comp)  or  "principal"  stresses,  sp  ,  at  any  point: 

tan  2.1    =   2v/s;  ...........................................................................  (19) 

&nd,  for  the  max  stress, 


=   s/2 


0?/2)2 


(20) 


where  v  =  the  unit  vert  or  hor  shear,  and  s  =  the  unit  hor  tensile  or  comp 
stress,  at  the  given  point. 

*  If  there  is  a  load,  L,  upon  B  (as,  for  instance,  in  the  case  of  uniform 
loading)  we  have  V  >  V,  and  V  —  V  =  L;  and  there  are  two  couples  of 
vert  forces,  with  moms,  respectively:  Vx  and  (V  —  V)  xf,  where  x'  =  dist 
from  sec  1  to  gravity  center  of  L.  Here  we  have,  for  sec  1,  v'  =  V'/b  d'; 
and,  for  sec  2,  v  =  V/b  d'. 


1126  CONCRETE. 

54.  But,  neglecting    the  tensile    strath  of   the    cone,  we 

have,  in  beams 'with  tension  reinfmt  of  straight  bars,  and  for  points  betw 
the  neutral  axis  and  the  steel,  8  =  0;  whence  : 

tan  2  A  _=    oo;         2  A    =  90°;         A    =   45°; 

8p  =    V  &  =   v   =   V/bd' (21) 

55.  Hence,  betw  the  neut  axis  and  the  steel,  we  should  provide  against 
tensile  unit  stresses,  sp  =  V/b  d\  acting  in  parallel  directions  form- 
ing angles  of  45°  with  the  neut  axis. 

56.  Other  things  being  equal,  this  provision  is  preferably  made  by  means 
of  rods,  placed  liRe  the   diag-    tension    members  of    a    Pratt 
bridge  truss,  Figs  76,  86,  96,  p  693,  and  forming  angles  of  45°  with  the  hor. 

57.  Very  commonly,  the  tension  rods,  at  each  end,  in  a  hor  dist  about 
equal  the  depth  of  the  beam,  are  bent  upward  to  form  an  angle  of  45°  or 
thereabouts  with  the  axis  of  the  beams. 

Adhesion.     Seep  1111. 

58.  Unit  of  adhesion.     Let 

z  =  a  given  portion  of  the  length  of  the  beam; 

t    =  T'  —  T  =  the  increase,  in  total  tension,  T,  in  the  steel,  in  the  Igth,  x; 
V  =  the  total  vert  shear  in  the  cross  section; 
d'  =  the  dist  betw  T  and  the  cen  of  comp  of  the  cone; 
U  =  t/x  =  the  bond  stress,  per  unit  of  x; 
m  =  the  number  of  rods; 
a   =  the  circumference  of  one  rod 

=  the  circumferential  contact  area  of  one  rod,  per  unit  of  x; 
u    =  U/m  a  =  the  bond  stress,  per  unit  of  a. 

Then  (see  H  50),  t  d'  =  V  x;  t  =  V  x/d'\   U  =  t/x  =  V  x/d'  x  =  V/d'\  and 
u   =    U/ma    =    V Id' ma (22) 

59.  For  given  values  of  the  bond  stress,  U,  per  unit  of  length,  and  of  the 
bond  stress,  u,  per  unit  of  circumferential  contact  area,  the  product,  m  a 
—   U  /u  (  =  total  circumferential  area  per  unit  of  length)  in  a  given  case, 
is  constant;  but  the  cross  sec  area,  weight   and   cost  of  the   rods  increase 
as  the  square  of  a.     Hence,  for  a  given   total   adhesion,  numerous   small 
rods  are  more  economical  than  fewer  larger  rods;  but  there  is,  of 
course,  for  each  case,  a  practical  limit  to  this  economy. 

Continuous  beams. 

60.  Floor  systems  are  usually  composed  of  slabs  and  beams  continuous 
over  supports;  and,  if  the  negative  bending  moments  over  the  supports 
(producing  tension  at  top  of  beam)  are  amply  provided  for,  by  reinfmt  near 
the  top,  and  if  the  supports  are  unyielding,  or  exactly  equal  in  their  yielding, 
advantage  is  usually  taken  of  the  reduction  in  the  positive  bending  moms 
(at  and  near  cen  of  span)  due  to  continuity. 

61.  Where  floor  slabs  are  laid  continuously  over  the  supporting  beams, 
it  is  usual  to  assume  WL/10  =   wL2/lQ  as  the  max  bending  mom,  where 
L   =    span;   W    =    total  load  on  span;  w  =   W/L  =  load   per  unit  of  L. 
Beams,  continuous  over  the  supports,  may  have  a  like  value  used  in  design, 
if  the  beams  are  amply  reinfd  at  top  and  over  the  supports. 

62.  On  the  score  of  safety,  it  is  frequently  specified  that  beams, 
slabs,  etc,  shall  be  regarded  as  non-continuous  over  supports,  this  practice 
requiring  us  to  provide,  at  cen  of  span,  against  greater  (positive)  bendg 
moms  than  if  the  beam  were  continuous  over  supports;  but,  on  the  other 
hand,  few  if   any  beams    are   wholly  non-continuous;  i  e,  even  where  the 
beam  is  supposed  to  be  non-continuous,  there  are  negative  bendg  moms 
over  the  supports,  due  to  the  width  of  the  support  and  to  the  presence  of 
loading  upon  the  beam  over  the  support.     Such  moms  require  reinfmt  at 
top,  over  and  near  supports. 

63.  Hence,  while  it  is  advisable,  in  the  case  of  non-continuous  beams,  to 
calculate  the  positive  center  bendg  mom  upon  the  assumption  of  absolute 
non-continuity,  the    condition  of    even  non-continuous  beams,  over    their 
supports,  should  be  carefully  investigated,  and  provision  made  for  any 
aegative  moms  there  found, 


REINFORCED    BEAMS. 


1127 


64.  I>ouble  Reinforcement.  The  necessity,  under  certain  condi- 
tions, of  reinfg  against  negative,  as  well  as  against  positive  moments  (11  62) 
gives  rise  to  cases  (Fig  6)  where  reinfmt  appears  near  both  top  and  bottom 
of  the  section.  For  brevity,  that  on  the  side  which,  under  positive  mom, 
is  under  compression,  will  be  called  "compression  reinft." 


kd 


o 


t's/n 
Fig  6.     Double  Reinforcement. 

65.  In  addition  to  the  symbols  of  K  5,  p  1115,  let 
asf  =  cross  section  area  of  comp  reinft; 

p'  =  ag'/ac   =   ag'  /b  d   =   steel  ratio  for  comp  reinft; 
fs'    =  unit  stress  in  comp  reinft; 

C"    =  total  stress  ......      ; 

311   =  dist  from  '     to  nearest  face  of  beam; 

z      =     "       "  comp  resultant,  C  +  C',  to  nearest  face  of  beam. 

66.  Then,  (neglecting  the  slight  diminution  of  ac  by  the  presence  of  cts') 
f6r  position  of  neutral  axis  : 

k  =  y  2  n  (p  +  p'  d"./d)  +  ri*  (p  +  p')2  —  n  (p  +  p');  ..................  (24) 

for  position  of  compression  resultant  : 
fc3  d/3  +  2  p'nd"  (k  —  d"/d) 


(26) 


for  arm  of  resisting  couple  : 

jd   =   d  —  z; 
for  fiber  stresses: 

6  Af*/b* 


fs   =    M/pjbd1* 


(k  —  d"/d)  (1  — 
nfc(l—k)/k 


•***\**m  j 


(28) 

fs'  =    n/c  (k  —  d"Jd)/k (29) 

METHOI>S  OF   REINFORCEMENT. 

1.  The  commonly  accepted  theory  of  reinfd  cone  beams  re- 
quires longitudinal  tension  reinfmt  near  the  bottom*  of  the  beam,  and  diag 
tension  reinfmt  at  45°,  nof  only  betw  the  hor  reinfmt  and  the  neutral  axis, 
but  extending  upward  into  the  region  of  compression,  in  order  to  take 
advantage  of  the  superior  adhesion  due  to  the  compression  there.  It  also 
requires,  usually,  tension  reinfmt  near  the  top,*  at  points  over  or  near  the 
supports. 

See  mi  60,  etc,  p  1126. 

*  The  terms  "bottom"  and  "top"  are  here  used  as  referring  to  a  beam 
supported  at  the  ends,  and  loaded  on  top,  where  the  major  portion  of  the 
bottom  is  in  tension.  In  a  cantilever,  of  course,  this  is  reversed. 


1128 


CONCRETE. 


2.  Numerous  trussed  systems  (p  1133)  have  been  designed,  in  order 
to  meet  this  requirement,  and  these  are  in  extensive  use  where  the  depths 
of  the  beams  are  sufficient  to  admit  them  and  where  the  loading  is  such  as 
to  require  them. 

3.  Frequently,  vertical  st irru;>s  are  substituted  for  the  diag  members, 
or  used  in  conjunction  with  them;  or  the  trussing  is  effected   by  simply 
bending  some  or  all  of  the  hor  bottom*  bars  upward,  usually  at  45°  or  there- 
abouts. 

4.  Under  light  loading,  the  truss  feature  is  often  omitted,  and  the 
reinfmt  consists  simply  of  longitudinal  bars  near  the  bottom*  of  the  beam. 

5.  Where  the  beam  is  both  shallow  and  broad,  as  in  floor  slabs,  the 
few  longitudinal  bars,  used  in  the  beam,  are  replaced  (1)  by  numerous  and 
comparatively  slender  rods,  supplemented  by  similar  or  lighter  rods,  crc.s.s- 
ing  them  at  right  angles  and  welded  or  wired  to  them  at  their  intersections; 
or  (2)  by  webbing,  such  as  wire  cloth  or  "expanded  metal." 

See  11f  34,  etc. 

Bar  Reinforcement. 

6.  For  a  given  wt  of  metal,  small  bars  give  a  greater  adhesion  area, 
and  therefore  a  greater  total  adhesion,  than  larger  bars   (1f  59,  p   1126); 
and  the  stresses  are  distributed  over  a  larger  area  of  cone.     Besides,  with 
small  bars,  a  larger  proportion  of  the  metal  can  be  brought  down  to  the  min 
allowable  dist  from  the  bottom*  of  the  beam.     Within  certain  limits,  small 
bars  are  more  conveniently  handled  than  larger  bars.     The  bars  used  are 
seldom  <  J4  inch  or  >  2  ins  diam,  and  they  usually  range  betw  %  and  1 J4 
inch.     In  deep  girders,  two  or  more  rows  of  small  bars  are  usually  prefer- 
able to  one  row  of  larger  bars. 

7.  In  vert  reinfmt,  before  completion,  the  free  ends  of  the  rods 
project  from  the  already  imbedded  mass  of  the  work,  and  accidental  blows, 

rn  these  exposed  ends  of  the  rods,  may  be  transmitted  to  the  portions 
ady  imbedded  in  cone,  affecting  the  adhesion  there.     In  this  respect 
also,  light  rods  are  preferable,  since  they  are  less  capable  of  transmitting  the 
effects  of  such  blows. 

8.  High-carbon  steel  rods,  with  their  high  elastic  limits,  permit 
the  use  of  smaller  sections  for  a  given  number  of  rods  and  given  total  stress; 
but  they  are  more  brittle  (when  of  inferior  quality)  than  softer  rods,  and 
are  not  readily  bent  cold,  to  desired  shapes.     The  smallness  of  the  sections 
commonly  used,  and  the  protection  afforded  by  the  cone,  render  brittleness 
less  objectionable  in  reinfd  cone  work  than  in  most  other  work  where  steel 
is  employed. 

9.  Since  the  elastic  modulus,  of  rolled  steel  and  iron,  is  nearly  the  same 


(say  30,000,000  Ibs/sq  inch)  for  all  grades,  these  all  stretch  about  equally, 
per  unit  of   length,  under   equal    unit   stresses;    but   steel  with  high 

Uts./aq,  in. 

60,000 
50,000 

^ 



— 

«*&. 

..     i 

^c£— 

40,000 
30,000 
20,000 
10,000 
0 

A 

&?' 

$ji& 

$ 

jf'   <\ 

/ 

3           0.5 

15           2           25           8           3.5 

"Elongation,  inches,  in  iooo-inches. 
Fig-  1.     Plain  and  Twisted  Rods. 


*  See  foot-note  on  previous  page. 


REINFORCING   BARS.  1129 

elastic  limit,  by  permitting  the  use  of  smaller  sections  and  therefore 
higher  unit  stresses,  renders  elongation  more  probable,  with  the  accom- 
panying cracking  of  the  cone,  and  lateral  contraction  of  the  steel,  which 
endangers  the  adhesion.  On  this  account,  it  is  sometimes  specified 
that,  where  the  elastic  limit  exceeds  a  certain  min  (say  40,000  Ibs/sq  inch) 
deformed  bars,  1JU  15  etc,  shall  be  used.  At  30,000  Ibs/sq  inch,  steel  stretches 
about  0.10  per  cent;  at  50,000  Ibs/sq  inch,  about  0.17  per  cent. 

Cold  working  raises  the  ultimate  strength  and  the  elastic  limit,  but 
slightly  lowers  the  elastic  modulus;  see  Fig  1,  representing  tests  at  Water- 
town  Arsenal  (Tests  of  Metals,  1904,  p  397)  on  plain  and  cold-twisted  steel 
bars,  %  inch  square.  Gaged  lengths,  10  inches.  The  twisted  bar  had  L 
twist  in  8  inches.  Similar  results  were  shown  in  tests  made  at  Watertown 
Arsenal,  July  12,  1902,  and  published  by  Ransome  Concrete  Co,  See  1  21. 

Square  bars,  of  inferior  steel,  are  twisted  hot,  and  are  more  brittle. 

10.  Plain  round  steel  bars  are  very  generally  used  for  reinforce- 
ment in  America,  and  still  more  generally  in  Europe.     Square  bars  also 
are  used,  but  are  less  conveniently  handled.     Flat  bars  have  been  found 
deficient  in  adhesion. 

11.  In  order    to   increase   the    resistance  of  plain    bars  to 
being  pulled  thru  the  cone,  they  are  frequently  bent  up  at  right  angles  (or 
bent  over  at  180°  so  as  to  form  a  hook)  at  their  ends. 

12.  "Anchorage,  furnisht  by  short  bends  at  a  right  angle,  is  less  effective 
than  hooks  consisting  of  turns  at  180°."     J.  C. 

13.  For  the  same  purpose,  (^  11),  the  bars  may  be  threaded  at  their  ends, 
and  provided  with  steel  anchor  plates,  secured  by  nuts.     Such  plates 
should  be  large  enough  and  thick  enough  to  withstand  pulls  due  to  the  full 
tensile  strength  of  the  rods.     In  designing  such  plates,  Prof.  L.  J.  Johnson 
assumes  a  crushing  strgth,  in  the  cone,  of  900  Ibs/sq  inch,  and  a  fiber  stress, 
in  the  anchor  plate,  of  25,000  Ibs/sq  inch.     Several  rods,  side  by  side,  pass 
thru  a  common  large  plate  at  each  end,  which  serves,  also,  to  hold  the  rods 
in  their   relative   positions  while  the  cone  is  being  placed.     Nuts,  on  the 
inside,  holding  the  anchor  plate  to  a  firm  bearing  against  the  outside  nuts, 
are  an  important  provision.     Room,  for  such  plates,  is  usually  found  in  a 
wall  or  column,  or  over  a  knee-bracket,  etc.     Otherwise,  in  order  to  give 
room  for  the  anchor  plate,  the  beam  may  be  deepened  locally,  or  the  rods 
bent  up,  near  their  ends.     When  bent  up,  the  rod  exerts  an  upwd  pres  upon 
the  cone,  near  the  bend.     This  increases  the  friction,  in  the  bent  portion, 
and  thus  reduces  the  pull  transmitted  to  the  anchor  plate. 

14.  "Adequate  bond  strgth,  thruout  the  length  of  a  bar,  is  preferable  to 
end  anchorage."     J.  C. 

15.  Also  for  the  purpose  of  increasing  adhesion  (or  rather  to  substitute, 
for  it,  a  "mechancial  bond")  "  deformed  bars,"  of  various  shapes  are 
used. 

16.  The   principal  claim,  in  favor  of  deformed  bars,  is  that   the 
"  mechanical  bond, "  which  they  offer,  is  the  sole  reliance  of  the  reinfmt, 
after  its  adhesion  proper  has  been  destroyed,  as  by  a  stress  exceeding  the 
adhesion,  by  infiltration  of  water,  by  concussion  either  during  or  after  con- 
struction, or  by  constant  and  rapid  alternations  or  reversals  of  loading,  in 
service.     Vert  rods  especially,  during  construction,  are  liable  to  accidental 
blows  upon  their  projecting  upper  ends;  and  such  blows  may  affect  the  ad- 
hesion of  the  portions  already  imbedded  in  cone. 

17.  On  the  other  hand,  it  is  pointed  9ut  that  innumerable  struc- 
tures,  with   plain   bars,    have   satisfactorily  withstood,   for  years,   service 
involving  such  vibration;  and  it  is  claimed  that  whatever  advantage  arises 
from  deformation  is  more  than  offset  by  the  slight  increase  of  cost.     Plain 
bars  are  of  course  free  from  patent  claims,  and  they  are  at  all  times  readily 
obtainable  in  the  general  metal  market. 

18.  The  projections,  9n  the  surfs  of  some  deformed  bars,  may  injure  the 
cone  covering  unless  this  is  of  considerable  thickness. 

19.  In  studying  comparative  tests  of  plain  and  deformed  bars,  attention 
should  be  given  to  the  richness  of  the  cone  mixture.     Unless  this  is  suffi- 
ciently rich  to  insure  the  complete  covering  of  each  bar  with  cem 
over  its  entire  surf,  the  adhesion  proper  will  not  be  fairly  developed,  and  the 
pulling  test  will  exhibit  chiefly  the  diff  in  "mechanical  bond,"  in  which,  of 
course,  the  deformed  bars  are  superior. 


1130 


CONCRETE. 


20.  "Deformed  bars  offer  a  suitable  means  for  supplying  high 
resistance."     J.  C. 

The  following  deformed  rods,  Figs  2,  are  in  more  or  less  general  use: 


(tt)  Ransome 
cold-twisted 
square 

(6)  Cold- 
twisted 
lug  bar 


rrffmmmt 


(/)  Diamond 
(Mueser) 


(.0)  Havemeyer 


(h)  Priddle 


Fig  2.     Deformed  Rods. 


21.  Ransome.     (a;  Square  steel  rods,  twisted  cold.     Twisted  either  a'. 
mill,  or  (conveniently  and  inexpensively)  on  the  work. 


REINFORCING   BARS. 


1131 


22.  Cold- twisted  lug-bar.  (6)  Square  bar,  with  angles  rounded,  to 
prevent  the  starting  of  cracks  in  the  cone,  twisted  (old.     The  lugs  are  de- 
signed to  resist  any  tendency  of  the  bar  to  untwist  under  tension.     For  effect 
of  cold  working,  see  1[  9,  p  1129. 

23.  Thacher.  (r)  Round  rods,  deformed  by  flattening  at  short  intervals. 
Cross  sec  area  practically  constant.     Changes  in  shape  made  by  means  of 
gradual  curves. 

24.  Corrugated  bars ;  (rf)  ordinarily  of  steel  with  yield  point  50,000 
Ibs/sq  inch  or  over.     Square,  round  and  flat. 

25.  Cup  bars,  (e). 

26.  Diamond  bar.     (/)  Rolled  round,  with  two  spiral  projecting  ribs 
of  equal  pitch  and  in  opp  directions  (dividing  the  surface  into  four  rows  of 
diamond-shaped   recesses)   and   two  opp  longitudinal   ribs,   at   the  points 
where  the  upper  and  lower  rolls  meet  in  manufacture.     Cross-section  area 
and  weight  =  those  of  plain  square  bars  of  like  denomination.     Claims  : 
uniform  cross  section   area,   uniform  elongation,   uniform  distribution   of 
bond;  projecting  ribs  aid  in  resisting  tension;  edges  rounded;  no  tendency 
to  untwist  under  tension. 

27.  Havemeyer  bar.     (g)  Square,  with  rounded  corners  and  pro- 
jections. 

28.  Priddle  Internal-bond  Bar.     (h)  Flat   bar,  perforated    and 
twisted,  and  the  slit  flanged,  as  shown.     Small  sizes  worked  cold;  larger 
sizes,  hot,     A  web  may  be  formed  by  passing  smaller  bars,  of  same  or  other 
pattern,  thru  the  slits. 

29.  The  monolith    bar  consists  of   a  hor   tension    member  with 
separate  diag  links.     In  section,  the  hor  member  resembles  a  heavy  rail 
with  two  heads  instead  of  head  and  flange.     Each  link  is  a  bar  of  round 
steel,  bent  over  at  top  and  thus  forming  two  parallel  diag  legs,  which,  at 
bottom',  are  bent  hor,  and  their  hor  portions,  one  on  each  side  of  the  hor 
member,  are  gripped  between  its  heads,  which  are  swedged  in,  at  those 
points,  for  the  purpose. 

Supports. 

30.  It  is  of  course  of  the  first  importance  that  the  longitudinal  rein- 
forcing bars  be  placed  and  kept  in  their  proper  positions.     If, 

as  finally  located,  they  are  too  high,  their  resisting  leverage,  d' ',  and  the  resistg 
moment  of  the  beam,  are  diminished.  If  they  are  too  low,  they  have  an 
insufficient  protective  depth  of  cone  below  them.  Various  devices  are  in 
use  for  holding  the  bars  in  position. 

31.  Stirrups,  Fig  3,  act  as  hangers  for  the  main  rods. 


Plan  \ 


(VsTVl 


t  Air  it 


Fig  3. 


Fig  4. 

Supports  for  Reinforcing  Bars. 


Fig  6. 


Fig  5. 


32.  Light  rods  are  sometimes  held  by  wire  supports,  Fig  4,  or  by 
cone  blocks,  about  1.2  or  2  ins  thick,  Fig  5. 

33.  Heavier  rods  may  be  supported  by  clamps.  Fig  6,  made  of  pieces  of 
%"  or  1"  channel  iron,  held  together  by  round-headed  stove  bolts,    W 
or  %"  diam,  placed  in  the  forms,  and  6  or  8  ft  apart. 

75 


1132 


CONCRETE. 


"Web"  Reinforcement. 

34.  Web  reinforcement  is  used  in  broad  and  shallow  slabs,  in  thin  walls, 
in  sewers  and  conduits,  in  columns,  etc. 

35.  The  simplest  form  consists  of  rods,  placed  at  right  angles, 

and  wired  or  welded  together  at  their  intersections.  The  heavier  or  main 
rods  are  of  course  so  placed  as  to  take  the  greater  stresses.  The  transverse 
rods  hold  the  main  rods  in  position  during  construction,  and  afterward 
distribute  their  tension  across  the  intervening  cone.  They  thus  offer  a 
mechanical  bond.  The  mesh  must  be  large  enough  to  pass  the  particles  of 
the  agg  used  in  making  the  cone. 

36.  Jean  Moiiier,  of  Paris,  used  such  webbing  in  the  reinforcement  of 
arches. 

37.  Expanded  metal.     Fig  7.     Sheet  steel,  slitted  and  opened  out 
into  diamond-shaped  panels.     In  sheets,  12  to  72  ins  wide,  8  to  12  ft  long; 
mesh  from  YJ'  to  6";  metal,  Stubs  gage,  No.  18  to  No.  4.      . 


Fig  7.     Expanded  Metal. 

38.  When  slab  reinforcement  is  furnisht  in  short  sheets,   these  must 
overlap  sufficiently  to  transmit  the  tension  from  one  sheet  to  the  next. 
The  lapping  uses  about  10  %  of  the  area  of  the  metal. 

39.  Clinton   wire  lath,  in  rolls  of  100  or  200  ft  or  more,  of  drawn 
steel  wires,  crossing  at  right  angles,  2^  inch  mesh,  electrically  welded  and 
reinfd  by  longitudinal  reinfg  warp  strands,  6  ins  apart,  and  made  up  each  of 
two  wires  cross-looped  and  twisted  over  each  crossing  strand;    and,  when 
desired,  by  transverse  V-shaped  stiffeners  of  No.  24  gage  steel,  fastened  to 
the  wires  at  intervals  of  about  8  ins.     Furnisht  plain,  japanned  or  galvd, 
in  36  inch  width. 

40.  Clinton  welded  wire;  No   3  to  No.  10  drawn  steel  wire,  plain 
or  galvd;  mesh,  3X8,      2  X  12,      3  X  12,     4  X  12  ins. 


Fig  8.     Rib  Metal. 

41.  Rib  metal,  Fig  8;  expanded  from  specially  rolled  steel  plates, 
ribbed  longitudinally.  Mesh  varying,  by  single  inches,  from  2  to  8  ins. 
Sheets  up  to  16  ft  long. 


REINFORCING    BARS. 


1133 


42.  Rib  lath,  Fig  9. 


Fig  9.     Rib-Lath. 

Trussed  Reinforcement. 

43.  In  general,  trussed  reinforcement  is  slightly  more  expensive  than 
plain  bar  reinfmt;  and,  if  shipped  in  rigid  built-up  units,  it  incurs  higher 
freight  charges  and  is  more  liable  to  damage  en  route;  but  it  has  the  great 
advantage  of  holding  the  bars  in  position  while  the  cone  is  being  placed,  and 


44.  In  the  lialin  trussed  bar,  Fig  10,  the  projecting  side  fins  are 
slit  away,  in  places,  from  the  central  portion,  and  bent  up,  as  shown.  The 
same  bar,  inverted,  is  used  over  the  supports. 


Cross  sec  at  cen.  Fig  1O.     Kahn  Bar. 

45.  Fig  11  shows  the  collapsible  Economy  Unit  frame. 


Fig  11.     "  Economy  "  Collapsible  Trusa 

Reinforcement  with  Structural  Shapes. 

46.  The    Melan    system,   invented    by  Joseph   Melan,  of  Austria- 
Hungary,  in  1892,  and  patented  in  the  United  States  in  1893,  comprises  a 
concrete  arch  in  which  iron  or  steel  beams  are  embedded.    For  small  spans, 
the  beams   are  usually   rolled   I-beams;  while,   for  spans  of  considerable 
length,  they  usually  consist  of  four  angles  latticed. 

47.  Where  a  structural  shape,  of  considerable  size,  is  imbedded  in  cone, 
to  form  a  beam,  so  that  the  steel  predominates  and  furnishes  most  of 
the  strgth  reqd,  the  cone  acts   chiefly  as  a   protecting   cover 
for  the  steel;  and  the  case  is  hardly  one  of  reinfmt  properly  so  called. 


1134  CONCRETE. 

48.  It  is  difficult  to  secure  perfect  filling,  with  cone,  of  the 
spaces  under  the  flanges  of  rolled  or  built-up  shapes.     In  such  cases,  each 
day's  work  slwuld  be  stopped  either  well  above  or  well  below  the  flange. 
Otherwise,  shrinkage,  under  the  flanges,  will  aggravate  the  difficulty. 

Column  Reinforcement. 

49.  Columns  are  reinfd  by  means  of  vertical  rods,  placed  near  the 
circumf  and  usually  wired  together  at  intervals,  or  by  circumferential 
(hooped  or  spiral)  wrapping,  or  both. 

See  Reinfd  cone  cols,  pp  1112,  etc. 

50.  In  tall  buildings,  the  column  rods  are  often  faced  at  the  ends 
to  give  good  bearing,  and  connected  by  loose  sleeves,  which  keep  the  ends 
in  proper  contact;  and  an  iron  or  steel  plate  is  placed  under  the  feet  of  the 
rods  in  the  footing,  to  distribute  the  load  more  evenly  over  the  cone  of  the 
foundation. 

51.  In  Mr.  C.  A.  P.  Turner's  mushroom  system  of  columns  and 
floors,  the  cols  are  splayed,  at  top,  to  increase  their  bearing  area,  and  the 
floor  reinfmt  consists  essentially  of  straight  members  (hor  or  nearly  so) 
radiating  from  the  cols,  and  joined,  at  intervals,  by  circular  or  polygonal 
members,  which  cross  the  radial  members  generally  at  right  angles.     Beams 
and  ribs  are  dispensed  with,  and  the  floor  is  of  uniform  thickness.     See  E  N, 
'09,  Feb  18,  p  178. 


DIRECTORY    TO   EXPERIMENTS. 


1135 


EXPERIMENT   AtfD   PRACTICE. 

Directory  of  Selected  Results,  pp  114O,  etc. 

Words  in  bold-face  type,  preceding  a  semicolon,  refer  to  one  of  two 
related  matters  ;  words  in  plain  type,  following  the  semicolon,  to  the  other 
one.  Numerals  and  letters  refer  to  the  records  of  experiment,  etc. 

Example.  Under  SANO  (below),  *4Sand,  character;  density  of 
jiortar,  8c,  e,  9d,  86c  "  refers  to  Experiments  8c,  etc,  which  give  informa- 
tion respecting  the  effect  of  (1)  character  of  sand  upon  (2)  density  of 
mortar.  Conversely,  on  p  1136,  we  find  "Mortar,  density  of — ; 
character  of  sand,  8c,  e,  9d,  86c." 


CEMENT. 


Cement, 
character  of  — ; 

water  reqd,  61  a 
Portland  A   natural — : 

water  reqd,  4  d 

strgth,  14  a,  19  a 

abrasion,  4  g 

permeability,  65  a 

electrolysis,  75  a 
silica  — ;  oil,  53  d 
typical  mix ;  86  / 
age  of  — ;  soundness,  29  a 

SiM> 

Sand, 

fineness  of — ; 

density  of  sand,  2  a,  8  h,  8  J< 
8k 

water  reqd,  61  a 

density    of    mortar,    8  c,    9  d, 
79  e 

strgth  of  mortar,  4  e,  8  a,  52  b, 
79  e 

permeability  of  mortar,  8  d,  9  e 

lime  reqd  for  waterproofg,  82  b 

sea  water,  8  g 

uniformity  coefficient ;  5  a 
grading  of — ; 

mortar,  8  e,  86  e 
shape  of  grains ; 

density  of,  sand,  8  i,  8  I,  94  a 
density  of — ; 


fineness  of — ; 

soundness,  29  b 

strgth  of  mortar,  4  / 

water  reqd,  4  d 

quantity  reqd ;  agg,  79  b,  d 
quantity  used; 

strgth  of  mortar,  8  a 

elastic  modulus,  70.5 
exposure ;    39  a,  b 
sulfuric  acid  in  — :  49  a 
chemical  action  of — ;  26  a, 

b,  c 


fineness,  2  a,  8  j,  8  k 
uniformity  coeff,  5  a 
shape  of  grains,  8  i,  94  a 
compacting,  2  a,  8  h,  8  i,  8  k, 

45  a 

character,  8  I 
mica,  87  a 

moisture,  2  a,  8  h,  8  I,  45  a 
mortar,  86  c,  d 
voids ; 

spheres  of  uniform  diam,45  6 

ACCIDENTAL 

Clay  in  cement ;  4  a 
Clay   A   loam  : 

strgth  of  mortar,  4  a,  34  a,  39  g, 

50  6,  52  a,  b,  56  a,  80  a 
absorption,  56  a 
plasticity  of  paste,  4  a 
density  of  paste,  4  a 
permeability,  4  a 
mortar  for  plastering,  4  a 
in  cone  for  columns,  92  a 


compacting ; 

density  of  sand,  2  a,  8  h,  8  i, 
8  k,  45  a 

fineness  of  sand,  8  k 
moisture  in  — ; 

density  of  sand,  2  a,  8  h,  8  I  . 

water  reqd,  61  a 
character ; 

density  of  sand,  8  I 

density  of  mortar,  8  c,  e,  9  d,  86  c 

strgth,  19  c,  39  g,  50  a,  52  a,  62  a 

absorption,  62  a 

impurities  in  — ;  19  c,  52  a 
clay  »V  loam  in  — ; 

strgth,  4  a,  34  a,  39  g,  50  b,  52  a, 
fe,  56  a,  80  a 

permeability,  4  a 

absorption,  56  6 
mica  in  — ;  79  a,  87  a 
friction  of  — ;  89  a 
percentage  of — ; 

electrolysis,  91  a 

abrasion,  4  g 
fusing  point;  89  b 
vs  screenings  ;  79  a-j 

density,  79  c 

permeability,  79  h,  j 

absorption,  55  a 
vs  crushed  limestone;  50 a 

IXOREDIEXTS. 

Clay  A-  alum ; 

permeability  80  a 
Mica  :  79  a,  87  a 
fciilfuric  acid:  6  a,  49  a 
Salt:  4  c,  19  a,  31  a 
<»ypsum;  51  a 
<»ypsum  «fr  lime:  51  c 
Calcium  chloride;  51  a,  b 
Lime ;  80  a,  82  d 
Lime  «&  gypsum;  51  c 


1136 


CONCRETE. 


Directory  to  Experiments,  pp  1140-1183 

MIXING  WATER. 

Water,  mixing  — . 

salt  in  — ;  4  c,  19  a,  31  a 
evaporation  of  — ;  9  a 
quantity  reqd : 

nat  &  Port  cem,  4  d 


cem,  character  of  — ,  61  a 
size  &  dryness  of  sand  grains, 

61  a 

mica,  87  a 
NII  If  uric  acid  in  — ;  strgth,  6  a 


MORTAR. 


Mortar, 

neat  «fc  sand  — ;  86  i 
consistency  of — ; 

fineness  of  cem,  4  d 

cinder,  83  a 

rate  of  setting,  4  d 

volume  of  cone,  21  a 

density,  61  a 

strength,  39  e,  61  a,  83  a, 

elastic  modulus,  61  6,  81  a 

permeability,  33  a,  47  c,  f,  61  a 

laitance,  61  d;  fire,  46  e 

preferable  — ,  61  e 

sea  water,  8  g 
richness  of  — ; 

volume  of  cone,  21  a 

density,  8  c,  9  d 

permeability,  8  d,  9  e 

sea  water,  8  g 
density  of—; 

percentage  of  voids,  9  6 

character  of  sand,  8c,e,9  d,  86  c 

richness,  8  c,  9  d 

clay,  4  a 

entrained  air,  evaporation,  9  a 
strength  of — ; 

fineness  of  cem,  4  / 

proportion  of  cem,  8  a 

exposure  of  cem,  39  a,  39  6 

character  of  sand,  4  e,  8  a,  86  d 

clay,  4  a,  34  a,  39  g,  50  b,  52  a,  6, 
56  a,  80  a 

salt,  4  c 

sulfuric  acid,  6  a 

consistency,  39  e 

hand  and  machine  mixing,  39  c 

treatment  of  briquet,  39  d 
permeability  of — ; 

character  of  sand,  8  d,  e,  9  e 

richness,  8  d,  9  e 

clay,  4  a 

diminution  of  —  with  time,  8  / 


cone ; 


plasticity  of  — ;   4  a 
soundness  of — ; 

cement,  29  a,  6 
abrasion  $40 
expansion  of  — ;  4  h 
lime  in  — ;  82  a 
sal  ammoniac  in  — ;  47  I 
briquet,    treatment    of  — ; 

strength,  39  d 
protection  of  metals  by  — ; 

in  water ;  4  ft,  8  / 

sea  — ,  4  6,  7  a,  8  g 
for  plastering; 

clay  in  — ,  4  a 
aeration : 

rate  of  setting,  84  a 
proportion  of — ,  in 

strgth,  79  / 

density,  79  / 

permeability,    13  b",    43  a,    79  g 

volume  of  cone,  21  a 

PROPORTIONS. 

Proportions ; 

density  of  concrete,  9  c 

elastic  modulus,  81  a 

strength,  14  a,  15  a,  18  a,  196 

shear,  81  6 

adhesion,  64  b 

strgth  of  columns,  35  a 

permeability,      9  /,  g,      13  a,  b, 

25  a,  43  a,  65  a 
thermal  conductivity,  46  b 
electrolysis,  91  a 
Grading ; 

distribution,  47  d 
cement  reqd,  79  d 
density  79  d 
permeability,  93  a 
transverse  strength,  72  a 


AGGREGATE. 


Aggregate; 

fire,  41  d 
proportion  to  mortar; 

volume  of  cone.  21  a 
addition  of — ; 

retardation  of  setting,  84  a 
dirt  in  — : 

strgth,  19  c 
weight  of  — ;  3  a 
density  of — ;  3  a 

gravel  <fe  broken  stone,  8  I,  14  a 

compacting,  21  c 
voids  in  — ; 

spheres  of  uniform  diam.  45  b 


size  of — ; 

cem  reqd,  79  6 

permeability,  79  t 

density,  81.  79  6;    strgth,  79  6 

elastic  modulus,  70.5 
kind  of—; 

density,  8  I 

proportions,  17et 

permeability,  79  g,  79  / 

strgth,  19  6,  35  a,  83  a 
gravel ;  8  I,  79  a 

strgth,  39  /,  83  a 

fire,  41  c,  70  f 

permeability,  9  g 


DIRECTORY   TO    EXPERIMENTS. 


1137 


Directory  to  Experiments,  pp  1140-1183. 


stone  vs  gravel; 

permeability,  79  j 

density,  14  a,  79  c 

strgth,  14  a,  79  c 

fire,  41  c 
granite ;  83  a 
limestone : 

water,  69  a 

strgth,  83  a 

sandstone  vs  shale;  11  a 
quartz;  expansion,  70 / 


AGGREGATE.— Continued. 

Screenings,  stone  — . 

grading;  86  b 
Screenings,  gravel  — , 

density ;  86  a 
Cinder  cone; 

strgth,   15  a,  23  a,  83  a 
fire,  41  e 

thermal  conductivity,  46  b 
consistency,  23  a,  83  a 
proportions ;  strength,  15  a 


CONCRETE. 


MIXING. 

Mixing ; 

distribution  of  sizes,  47  d 
freezing  weather,   44  a 
shrinkage,  21  a;    fire,  46  e 
rate  of  — ,  39  c 

hand    «fc    machine  — ;    22  a, 
39  c 

continuous;  27  a 

thoro;   strength,  12  a 
Re-tempering  ;  28  a 

FORMS,  PLACING, 
COMPACTING. 

Forms ; 

coated  with  soft  soap,  32  a 
Placing, 

freezing  weather,  44  a 

dropping  from  height,  33  a 

delay  in  — ,  20  a 
Compacting ; 

density,  17  a    21  b,   21  c,   45  a 

fire,  46  e 

SETTING. 

Setting, 

expansion  during  — ;  4  h 
rate  of  — ; 

salt,  4  c;    consistency,  4  d 

aeration,  84  a 

addition  of  agg,  84  a 

gypsum,  51  a 

lime  and  gypsum,  51  c 

calcium  chloride,  51  a,  51  & 


Age; 


AGE. 


th,    12  a,    14  a,    18  a,    81 


strgth,    12 
86  g,  h,  i 


elastic  modulus,  61  b 
permeability,  61  c,  78  b,  79  / 

I,AITANCE. 

Lai  tan  ce  ; 

consistency,  61  d 
permeability,    47  fc,    60  a,    61  d 
strgth,  61  d 
thickness  of  — ;  61  d 

REGRINDING. 

Regrinding;  31  c,  77  a 

C8 


FINISH. 

Finish  ;  24  a,  32  a,  44  6 

water-tight  — ;  47  h,  57  a,  93  a 
Soap  and  alum  mixture ;  47  h 
Paint ;  66  a 

PROPERTIES,  BEHAVIOR. 
Density ; 

fineness  of  sand,  79  e 

sand  vs  screenings,  79  c 

gravel  vs  stone,  79  c 

size  of  agg,  79  b 

proportions,  9  c,  17  a 

grading,  79  d 

lime  paste,  82  d;   clay,  4  a 

consistency,  61  a 

mortar,    proportion  of  — ,  79  / 

compacting,  21  6 

permeability,  72  b,  79  g 

durability,  72  6;   strgth,  72  6 

plasticity,  72  6 
Voids ;  45  b 
Volume;  21  a 
Shrinkage  ;  21  a,  42  a,  73  a 
Absorption  ;  55  a 

character  of  sand,  62  a 

sand  vs  screenings,  55  a 

clay  and  loam  in  sand,  56  6 

strgth,  62  a 
Ductility;   16  a,  30  a,  36,  38,  48, 

81  e,  f 

Flow  ;  58  a 
Durability ;  72  6 
Plasticity ;  72  6 
Soundness :    oil,  68  a 
Abrasion ;  4  g 

Strength. 
Strength ; 

ingredients,  50  a 
nat  and  Port  cem,   14  a,   19  a 
typical  mix,  86  / 
sand,  character  of  — ,  62  a 
sand,  fineness  of  — ,  52  6,  79  e 
sand,  grading  of  — ,  86  e 
sand  vs  crushed  limestone,  50  a 
proportions,  14  a,  18  a,  19  b 
agg,  character  of  — ,   19  b,  83  a 
agg,  size  of  — ,  39  /,  79  b 
gravel  vs  stone,  14  a,  79  c 
sandstone  vs  shale,   11  a 
cinder  cone,  15  a,  23  a 


1138 


CONCRETE. 


Directory  to  Experiments,  pp  1140-1183. 
CONCRETE. — Continued. 


screenings,  86  6 

mica,  87  a 

proportion  of  mortar,  79  / 

dirt  in  sand  and  agg,  19  c 

clay  and  loam,  34  a,  39  g,  52  6, 
56  a 

clay  and  alum,  80  a 

lime,  80  a 

consistency,  61  a,  83  a 

salt,  19  a 

mixing,   12  a,   22  a,   27  a 

re-tempering,  28  a 

delay  in  placing,  20  a 

laitance,  61  d 

re-grinding,  77  a 

age,  12  a,  14  a,  18  a,  81  g,  86  i 

cold,  19  a 

density,  72  a,  b 

fire,  46  d,  70  d  to  f 

oil,  63  a  to  c,  68  b 

absorption,  62  a 

reinforcement,  percentage  of  — , 
81  g 

columns,  35  a 

reinforced  beams,  81  g,   h 

uniformity,  86  g,  h 

safe,  9h,  12  b 

compressive  — ,  85  a,  86  i 

tensile  — ,  85  a,  86  i 

transverse  — ,  85  a 

torsional  — ,  81  c 

shearing  — ,  81  6,  e 

shearing  — ,  in  beams;  81  h 
Fatigue  ;   16  a,  48  a,  76  a  to  e 
Unit  stress ; 

unit  stretch,  67  a,  81  a 

Elastic  Properties. 
Elastic  properties ;  67  a,  81  a 

Potenzgesetz   (law  of  powers), 
67  a 

fire,  70  c 

neutral  axis,  position  of — ,  83  a 
Elastic  limit; 

adhesion,  88  a;  fatigue,  76  c 
Elastic  modulus  ;   81  a 

size  of  agg,  70.5 

proportions,  70.5,  81  a 

consistency,  61  b,  81  a 

age,  61  6 

fatigue,  76  c;  fire,   70  c 

columns,  35  a 

Permeability. 
Permeability :  47  a  to  I,  78  a  to 

d,  79  g,  82  a 

cem,  Port  &  nat  — ,  65  a 
proportions,  9  /,  g,  13  a,  b,  25  a, 

43  a,  65  a 

excess  mortar,  13  6,  43  a,  79  g 
aggregate,  79  g,  i,  j 
grading,  93  a 
gravel  with  sand,  9  g 
sand,  screenings,  stone,  gravel, 

79  j 
clay,  4  a 


clay  &  alum,  80  a 
lime,  80  a,  82  a,  c 
lime  &  sand,  82  6 
consistency,   33  a,   47  c,  /,   61  a 
laitance,  47  b,  60  a,  61  d 
density,  72  b,  79  g 
waterproofing,  47  h,  80  a 
soap  and  alum  mixture,  47  h 
finish,  47  h,  57  a,  93  a 
reinforcement,  47  /,  g 
sunshine,   47  e 

pressure,  25  a,  78  b,  c,  d,  79  g 
percolation,  47  b,  60  a,  65  a 
thickness,  79  j 
age,  61  c,  78  b,  79  j 
tanks,  33  a,  57  a 

EXTERNAL  INFLUENCES. 

Electrolysis ;  75  a,  91  a 

Sunshine ;  permeability,  47  e 
Air; 

corrosion,  59  a,  b 
shrinkage  and  expansion,  73  a 
steam  and  carbonic  acid; 

corrosion,  40  a,  6 
Water ;  4  b,  8  f 

shrinkage  &  expansion,  73  a 

limestone  cone,  69  a,  b 

hardness  of  mortar,  37  c 

strgth,  23  a 

adhesion,  26  a,  37  c 

corrosion,  26  a,  37  c,  59  a,  b 
sea  — ;  7  a,  31  a,  b,  c,  49  a,  90  a 

corrosion,  59  a,  6  - 

fineness  of  sand,  8  g 

placing  in,  4  c,  31  a,  6 
Pressure ; 

permeability,   786,   c,   d,   79   g 
Percolation  ; 

permeability,  8  /,  47  b,  60  a 
Sewage;  37  c 

Oil ;  53  a  to  /,  63  a  to  c,  68  a,  6 
Abrasion ;  4  g 

Heat  and  Cold. 
Freezing  weather; 

mixing,  44  a;  placing,  44  a 

finished  work,  19  a,  44  a,  90  a 
Expansion  coefficient;  1  a,  10  a 
Thermal   conductivity;  46  />, 

70  g,  i 
Fire;  41  a-e,  46  a-e,  70  a-i 

San  Francisco,  71  a-d 

aggregate,  41  c,  d,  e 

gravel  and  broken  stone,  41  c 

cinders,  41  e 

disintegration,  70  d-f 

strgth,  46  d,  70  d-f 

elastic  properties,  70  c 

requirements,   46  e 

reinforced  cone,  41  b,  46  c,  e,  70  h 

COLUMNS. 

Columns ; 

clay  in  cone  for  — ,  92  a 
strgth  of  — ;  35  a 
elastic  modulus  ;  35  a 


DIRECTORY   TO   EXPERIMENTS. 


1139 


Directory  to  Experiments,  pp  1140-1183. 


REINFORCEMENT,  METALS, 

Concrete,  reinforced  — ; 

shear,  81  6,  h 
stresses  in  — ,  81  g,  h 
fire,  41  6,  46  e 
Reinforcement ; 

strgth,  81  h 
fire,  46  c 

permeability,  47  g 
adhesion  &  friction  :  64  a,  b, 

81  d,  h,  88  a 
plain  &  deformed  bars,   64  a, 

74  a 

high  &  medium  steel,  88  a 
disturbance,  64  a,  76  d 
proportions,  64  b 
time,  26  d 
elastic  limit,  88  a 


ADHESION,  CORROSION. 

fatigue,  76  d 

exposure,  26  a,  37  a,  6,  c 
corrosion  of — :  2  6,  26  a,  6  c 

37  a,  6,  c,   40  a,  6,  44  c,  47  L 

54  a,  59  a,  6 

conductivity  of — ;  70  i 
electrolysis  ;  75  a,  91  a 
disturbance  of—;  47  /,  64  a, 

76  d 
plain  »V  deformed  — ; 

adhesion,  64  a,  74  a 
high  »V  medium  steel ; 

adhesion,  88  a 
percentage  of  — ;  81  g 
strength  of  — ;  81  h 
stirrups ;  81  h 


1140 


CONCRETE. 


Experiment  and  Practice* 
Selected  Results. 

See  Directory,  pp  1135,  etc. 
Order  of  arrangement. 

The  features  entering  into  the  manufacture  and  behavior  of  concrete  are 
so  numerous,  and  in  the  reports  of  experiments,  etc,  they  are  unavoidably 
so  interlaced,  that  it  has  been  found  impracticable  to  group  the  several  items 
in  the  body  of  the  text  in  satisfactory  order  below. 

Most  of  our  "selected  results"  are  therefore  here  placed  approx  in  the  order 
of  their  dates  of  publication,  and  furnisht  with  a  directory,  pp  1135  etc,  by 
means  of  which  any  particular  subject  may  be  promptly  found.  The  direc- 
tory is  arranged  rationally  (i  e,  not  alphabetically),  and,  as  far  as  practi- 
cable, in  the  order  followed  in  the  text  (pp  930-947  k,  1084-1134),  referring 
to  cement,  sand,  mortar,  aggregate  and  concrete,  plain  and  reinforced. 
The  items,  covered  by  any  one  publisht  statement,  are  given  a  common 
number,  and,  under  this  common  number,  the  several  paragraphs  are  indi- 
cated by  letters.  These  letters  usually  distinguish  also  betw  the  several 
features  covered  by  the  common  number. 

Thus,  under  Expt  8,  we  have  a  number  of  conclusions  reached  by  R. 
Feret:  under  8  a,  conclusions  respecting  strength  of  mortar  as  affected  by 
proportion  of  cement  and  fineness  of  sand;  under  8  c,  conclusions  respecting 
porosity  and  permeability  as  affected  by  fineness  of  sand  and  richness  of 
mortar,  etc,  etc. 

In  the  directory,  semicolons,  in  general,  are  used  to  distinguish  between  two 
different  but  related  ideas.  Thus:  '"Strength;  fineness  of  sand"  and 
"Sand,  fineness  of — ;  strength,"  refer  to  items  giving  information  re- 
specting the  effect  of  fineness  of  sand  upon  strength  of  mortar  or  cone. 


1.  Bonriiceau,  Annales  des  Fonts  et  Chaussees,  1863,  p  181. 
1  a.  Expansion  Coefficient. 

Bar  iron 0.000 0123  5  per  deg  C;      0.000 006 86  per  deg  F 

Port  cem  Cone 0.00001370 0.00000760    "     "     " 


2.  John  C.  Trautwine,  Civil  Engr's  Pocket  Book,  1872. 

2  a.  Sand,  density ;  moisture,  compacting-. 

Specimens.  Ordinary  pure  sand  from  the  seashore,  both  dry  and  moist 
(not  wet),  see  table.  Sand  B  was  of  much  finer  grain  than  A.  C  consisted 
of  the  finest  grains  sifted  from  B. 

Treatment.  The  dry  sands  were  compacted  by  thoro  shaking  and  jar- 
ring; the  moist  sands  by  ramming  in  thin  layers. 

Results. 

Sand  A  Sand  B  Sand  C 

(coarse)  (finer)  (finest) 


Dry 


Moist 


Dry 


Moist 


Dry 


Ibs     Solid    Void    Ibs      Ibs     Solid    Void    Ibs      Ibs.  Solid  Void 


per 
cu 

ft 

% 

% 

per 
cu 
ft 

per 
cu 
ft 

% 

% 

per 
cu 
ft 

per 
cu 

ft 

% 

% 

Loose  

97 

59 

41 

86 

88 

53.4 

46.6 

69 

82 

50 

50 

Compacted 
Increase.  .  . 

112 
15 

68 
9 

32 
—9 

107.5 
21.5 

101.6 
13.6 

61.6 

8.2 

38.4 
—8.2 

103.5 
34.5 

98.5 
16.5 

60 
10 

40 
—10 

Percent...    15.5     15.2     22       25 


15.5  15.3     17.6      50       20.1     20       20 


2  b.  Corrosion.  10  years'  trial.  Dampness  absolutely  excluded  after 
setting.  Cements  protect  iron,  lead,  zinc,  copper,  brass.  Plaster 
of  Paris  protects  all  these  except  ungalvanized  iron. 


EXPERIMENT   AND   PRACTICE.  1141 

For  abbreviations,  symbols  and  references,  see  p  947 1. 

3    

3.  John  Watt  Saudemau.     last  C  E,  Vol.  liv,  1878,  p  260. 

3  a.  Aggregates  ;  density. 

Results  Ibsper  Percentage 

No.  cub  ft  of  voids 

1.  Broken  limestone,  mostly  3  inch 95  50.9 

2.  Screened  gravel,  from  small  pebbles  to  2.5  inch.  .  Ill  H         33.6 

3.  Equal  parts  of  Nos.  1  and  2,  well  mixed 113  Y^         34.0 

4.  Broken  sandstone,  4  to  8  inch 74  50.0 

5.  "  "  from  sand  to  4  inch 92  34.0 

6.  Equal  parts  of  Nos.  4  and  5,  mixed 91  M         36.0 

4    

4.  Eliot  C.  Clarke,  A  S  C  E  Trans,  Apr,  '85,  Vol  14,  p  163.     Expts 
for  Boston  Main  Drainage  Works. 

Results. 

4  a.  Clay.     The  addition  of  not  exceeding  one  part  of  clay  to  2  of  cem, 
gave  a  ' '  much  more  dense,  plastic  and  water-tight  paste,  convenient 
for  plastering  surfaces  or  stopping  leaky  joints,"  and,  in  general,  had  no 
markt  effect  upon  the  strength  of  Portland  and  natural  cem.     Mortars, 
made  with  sand  containing  10%  of  loam,  were  of  normal  strgth  at  6  and  12 
mos,  thp  of  only  about  half  normal  strgth  up  to  1  mo.     Clay,  in  cem,  is  "an 
almost  impalpable  powder,  with  particles  fine  enough  to  fill  the  spaces  be- 
tween the  particles  of  cem." 

4  b.  A  year's  saturation  in  fresh  or  salt  water,  and  in  contact  with 
oak,  hard  pine,  white  pine,  spruce  or  ash,  did  not  affect  the 
mortars. 

4  c.  Salt,  either  in  the  water  used  for  mixing,  or  in  that  in  which  the  cem 
is  laid,  retards  setting  somewhat,  but  has  no  important  effect  upon  the 
strength. 

4  d.  Consistency.  Excess  of  water  retards  setting.  Nat  cems 
need  more  water  than  Port;  fine-ground  more  than  coarse;  quick- 
setting  more  than  slow. 

4  e.  The  finer  the  sand,  the  less  the  strength. 

4  f.  With  sand,  fine-ground    cems  are  strongest;  coarse-ground 

are  strongest  neat,  especially  with  Portlands. 

4  g.  Port  resisted  abrasion  best  when  mixt  with  2  parts  sand;  nat  with 
1  part.  Resistance  diminished  rapidly  with  slight  variations  from  these 
proportions. 

4  h.  In  setting,  mortars  expand  >  1  part  in  1000. 

5    

5.  Allen  Hazen,  Mass.  State  Board  of  Health,  Report  '92,  p  550. 
Sharp-grained  sand. 

5  a.  Uniformity  coefficient  (u.  c.)p  947:          <2         <3       6  to  8 
Voids,  per  cent,  approx, 45  40         30 

6     

6.  E.  Carey,  Inst  C  E  Procs,  Vol  107,  '92,  p  55. 

6  a.  Sulfuric  acid ;  strength.     Neat  cem,  gaged  with  water  con- 
taining 5  %  acid,  had,  at  7  days,  only  27  %  of  the  strength  of  neat  cem 
gaged  with  water  free  from  acid. 

7    

7.  Dr.  Wilhelm  Michaelis,  Inst  C  E  Procs,  Vol  107,  '92,  pp  372,  375. 

7  a.  Disintegration  of   porous    cem  in  sea  water  shown  to    be 
due  to  the  action  of  sulfuric  and  hydrochloric  (muriatic)  acids,  contained  in 
the  magnesium  sulfates  and  chlorides  of  sea  water.     These  acids  leave  the 
weaker  base,  magnesium  (which  is  deposited  as  a  hydrate),  and  combine 
with  the  lime  of  the  cem,  expanding  and  disintegrating  the  cone. 


1142  CONCRETE. 

For  directory  to  Experiments,  see  pp  1135-9. 


8.  R.  Feret.     Annales  des  Fonts  et  Chaussees,  7e  serie,  Tome  IV,  '92. 

8  a.  Results.  Strength  of  mortar  increases  with  proportion  of  cem, 
and,  in  general  (especially  at  the  beginning  of  hardening)  with  size  of  sand. 

8  to.  Mortars  vary  widely  as  to  porosity.     Compare  9  d ,  9  e. 

8  c.  Porosity  increases  8  d.  Permeability  increases 

with  fineness  of  sand,  with  coarseness  of  sand, 

with  richness  of  mortar  with  richness  of  mortar. 

8  e.  Mortars  made  with  a  mixture  of  coarse  and  fine  sands  are  less 
porous  and  less  permeable  than  others. 

8  f.  The  permeability  of  mortars  subjected  to  continuous  percola- 
tion of  fresh  or  sea  water,  diminishes  rapidly;  but,  in  certain  cases, 
the  mortar  disintegrates  or  cracks. 

8  g.  To  avoid  disintegration  in  sea  water,  use  coarse  sand  and  plenty 
of  cem.  Mix  wet. 

8  h.  Density  of  sand;  moisture  and  tamping-.     Fig.  1. 


0.500 


0.04  0.08  0.12  0.16 


0.400 


0.300 


0.000 


0.500 


0.400 


0.300 


0.000 


0  0.04  0.08  0.12  0.16 

founds  of  Water  per  pound  of  dry  sand, 

Fig  1.     Moisture  and  Tamping. 

M.  Feret  used  (1)  a  very  fine  dune  sand  and  (2)  a  coarser  sea  sand.  Wm. 
B.  Fuller,  E  N,  '02,  Jul  31,  p  81,  used  a  bank  sand,  (1)  loose  and  (2)  tamped. 

From  these  results,  it  appears  that  the  addition  of  water  affecvs  the  vol 
of  the  sand*  in  two  opposite  ways;  (1)  by  insinuating  itself  betw  the  sand 
particles,  thus  increasing  the  vol  for  a  given  wt;  (2)  by  decreasing  the  fric- 
tion between  the  grains,  allowing  them  more  readily  to  take  up  the  positions 
of  closest  contact,  and  thus  diminishing  the  vol.  When  only  small  vols  of 
water  have  been  added,  the  first  of  these  effects  seems  to  prevail,  the  bulk 
increasing  until  the  vol  of  water  reaches  from  2  to  5  %  of  the  vol  of  dry  sand.* 
With  more  water,  the  lubricating  effect  prevails,  the  vol  diminishing. 


Loose 


10         20 


40         50 


60 


70 


90      100 


Tamped 
torefusctlQ 


10 


20        30        40         50        60         70        80         90 
Percentage  of  solid  in  given  volume  of  sand. 

Fig  2.     Compacting. 

8  i.  Shape  of  grain  and  tamping.     Fig.  2. 
*  See  foot-note  *,  p  946. 


100 


EXPERIMENT   AND   PRACTICE. 


1143 


For  abbreviations,  symbols  and  references,  see  p  947Z. 

Specimens.     Four  materials,  as  follows: 

a.  Granitic  sand,  rounded  grains;  c.  Broken  shells,  flat  grains; 

b.  Ground  quartzite,  angular  grains;      d.  Residue  from  6,  lamellar  grains. 
Each  of  the  four  materials  screened  to  the  same  granulometric  compoai- 

tion,  viz:  c,  0.5;  m,  0.3;  /,  0.2.f     (See  p  946.) 
Results.     See  Fig.  2. 
S  j.  Effect  of  size  of  main.     Fig.  3. 


383 


50 


100  150  200 

Meshes  per  linear  decimeter. 


250 


Fig1  3.    Size  and  Density.      A  =  Alexandre  ;  C  =  Candlot. 

Theoretically,  the  density,  in  a  sand*  or  gravel,*  composed  of  grains  of 
uniform  size,  should  be  independent  of  the  absolute  size  (f  30,  p  947  6);  but 
experimenters  have  obtained  contradictory  results,  showing  unimportant 
variations  of  density  with  size.  Thus  (T  &  T,  p  170),  if  sand  (except  very 
fine  sizes,  such  as  pass  a  sieve  with  74  meshes  per  linear  inch)  and  broken 
stone,  with  irregular  particles  of  approx  uniform  shape,  be  separated  into 
portions  containing  particles  of  uniform  size,  these  several  portions  will 
show  approx  equal  percentages  of  voids.  This  agrees  wifh  R.  Feret's  ex- 
periments (T  &  T,  pp  171  and  142),  Fig  3,  according  to  which  each  of  the  3 
sizes  (coarse,  medium  and  finef)  contained  50  %  voids.  M.  Feret's  results 
are  represented  by  the  hor  line  in  Fig  3.  On  the  other  hand  (Fig  3)  M. 
Candlot  (Feret,  Ann  des  Fonts  et  Chaussees,  1892,  2e  sem)  found  the  voids 
increasing  continuously,  and  M.  Alexandre  (ibid)  found  them  first  increasing 
a-nd  afterward  decreasing  as  the  size  grew  smaller. 

8  L .  Effect  of  sizes  of  grains,  and  shaking*  or  tamping. 
Loose  sand*  shows  densities  ranging  from  0.525  to  0.610,  the  max  density 
occurring  when  60  %  of  coarse  sandf  is  mixed  with  40  %  of  fine  sand,  with- 
out medium  sand.  In  sand  shaken  to  refusal,  the  densities  range 
from  0.600  to  0.793,  the  max  density  occurring  with  a  mixture  of  55  %  coarse 
with  45  %  fine;  no  medium. 


*  See  foot-note  *,  p  946. 
t  Classification  of  sizes. 


c.    Coarse 20 

m.  Medium 60 

/.     Fine 180 


Retained  on 

60             meshes  per  lineal  decimeter. 
180  


1144  CONCRETE. 

For  Directory  to  Experiments,  see  pp  1135-9. 

81.  Densities    of   loose    unscreened    sands    and  gravels; 
shapes  and  sizes  of  grains;  moisture. 


Wt  of 
pebbles 
con- 
tained, 

% 

Mechanical    Analysis 
of  sand  proper 

Dry 

sand 
Kg  per 
cu  M. 

Moist  sand 

Mois- 
ture 

% 

Kg 
per 
cu  M, 

Coarse 

Med. 

Fine 

Granitic 
rounded  grains  .  . 
Schistose  

1.0 
25.4 
6.6 

0.136 
0.359 
0.259 

0.723 
0.293 
0.412 

0.141 
0.348 
0.329 

1,586 
1,753 
1,600 

0.8 
1.2 

1.8 

1,495 
1,650 
1,332 

9.  Luigi  Lniggi  and  Valentino  C'ardi,   "Esperimenti  sulle  Calci, 
etc;"  Gemo  Civile,  Rome,  '93. 

Porosity,  permeability,  etc.     Safe  loads.     Twelve  years'  expts 
in  connection  with  harbor  works  at  Genoa,  Italy. 
Results. 

9  a.  In  mortar,  voids  are  due  partly  to  air  adhering  to  particles  of 
sand  and  agg,  partly  to  evaporation  of  the  water  used  in  mixing. 

9  b.  In  mortar,  volume  of  voids  may  vary  from  12  to  46  %  of  vol  of 
mortar. 

9  c.  Minimum  voids  (5  %)  in  cone  formed  with  700  Ibs  Port  cem, 
1  cu  yd  mixt  sand,  1  M  cu  yds  small  gravel. 

9d.  Porosity  increases  9  e.  Permeability  increases 

with  fineness  of  sand;  with  coarseness  of  sand; 

'     richness  of  mortar;  "    poorness  of  mortar; 

greatest  with  neat  cem.  least  with  neat  cem. 

Compare  8  c,  8  d. 

9  f.  Concrete  of  1150  Ibs  Port  cem,*l  cu  yd  mixt  sand,  1  M  cu  yds  small 
gravel,  carefully  mixt  with  just  enough  water  (about  %  cu  yd)  to  work  it 
up,  was  impermeable  under  40  ft  head  (17.3  Ibs/Q"). 

9  g.  Concrete  of  700  Ibs  Port  cem,  1  cu  yd  mixt  sand,  1  ^  cu  yds  small 
gravel,  made  into  a  hollow  cyl  with  shell  2  1A"  thick,  was  impermeable 
under  13  ft  head  (5.64  Ibs/D")  and  barely  permeable  under  27  ft  (11.7 
lbs/D").  Similar  cyls,  of  same  mixture,  without  the  gravel,  leaked 
somewhat  under  13  ft  and  easily  under  27  ft. 

9  Ii.  Safe  load  in  compression.  In  the  floors  of  the  graving 
docks,  1:2:3  cone  of  Port  cem,  sand  and  small  gravel,  safely  carries  107 
Ibs/Q"  ;  safety  factor,  15. 

10    

10.  »r.  Keller,  Thonindustriezeitung  '94,  No.  24. 

1C  a.  Expansion  Coefficient.     Temps  from  —  16°  to  +  72°  C   — 

+  3°  to  +  162°  F.     Gravel  (20  mm)  and  sand,  in  equal  parts. 

Mixture  of  sand  and  gravel,  parts 
0248 

0.0000101     0.0000104     0.0000095 
F...  0.000  0070     0.0000056     0.0000058     0.0000053 


Proportions  (1  part  cem)  to 
Coefficient,  per  degree  C. .  .0.0000126 


_  -a  -m       r 

11.'  Oeo.  W.  Rafter,  2d  Report  on  Genesee  R  Storage  Project,  '94. 
See  E  R,  '06,  Jan  27,  p  109. 

11  a.  Concrete  with  hard  sandstone,  gave  strength  50  %  greater 

than  where  shale  was  substituted. 


EXPERIMENT   AND   PRACTICE.  1145 

For  abbreviations,  symbols  and  references,  see  p  947*. 

12    

12.  L,eibbrand.     E  R, '94,  Nov  3. 

12  a.  Comp  strength ;  age.     Bridge   over   Danube  at   Munder- 
kingen.     Cone  1  :  2.5  :  5,  wet.     Cubes  20  cm  (8"). 

Very  thoroly  mixt  in  an  iron  cylinder  revolving  on  a  hor  axis  and  con- 
taining 40  steel  balls  weighing  together  660  Ibs.    Mixt  2  mins  dry,  3  mins  wet. 

Age  in  days 7          28  150  970         3285  (=  9  years) 

Comp  strgth,  kg/sq  cm .  .   202        254  332  520  570 

l'ba/sq  in 2870     3610         4720         7400         8100 

12  b.  Max  existing-  pressures,  in  bridge,  500  to  560  lbs/D". 

13    

13.  J.  Watt  Sandeman,   Inst  C  E  Procs,  Vol  121,  '95,  p  220. 

13  a.  "Watertight  eoiierete  walls  (pres   not  stated)   made  with 

1  part  cem  leaving  10  %  on  No.  120  sieve, 

2  parts  sand  with  27  %  voids, 

4.5  "    large  and  small  gravel  with  >  35  %  voids. 

13  b.  Where  agg  has  35  %  voids,  vol  of  mortar  should  be  50  %  of 
vol  of  agg. 

14     

14.  A.  W.  Dow,  U.  S.  Inspector  of  Asphalt  and  Cem.     Report  of  Engr 
Commsr,  Dist  of  Columbia,  '97,  p  165. 

14  a.  Compressive  strength. 

Specimens,  12-inch  cone  cubes,    dry;    rammed   in  cast    iron  molds; 
thoroly  wet  twice  daily. 

The  results  for  one  year  are  means  of  five  cubes ;  the  rest  are  means  of  two 
cubes.     Deduct  from  3  to  8  per  cent,  for  friction  of  press. 
The  materials  were  as  follows: 

Cement.  Portland  Natural 

Per  cent,  retained  on  sieve  of  100  meshes  per  linear  inch,       8.5  14 

Time  for  initial  set,  minutes 190  20 

"    hard  305  36 

Tensile  strength  as  follows,  Ibs.  per  square  inch: 

1  Day.     7  Days.     1  Mo.     3  Mos.     6  Mos.     1  Year. 

Portland,  neat 441  839 

3  parts  stan- 
dard broken  quartz,  248          429  398  428  474 

Natural,  neat, 96  180 

2  parts  stan- 
dard broken  quartz,  91          188  327  414  485 
Sand  used  in  concrete. 
No  residue  on  a  No.  3  sieve;  0.5  per  cent,  passed  No.  100.    Voids  44  per 

cent.,  with  4.4  per  cent,  water. 

Broken  Stone.     Gneiss.     Of  Nos.  6  and  12  (table  below)  3  per  cent. 

retained  on  2.5  inch  mesh;  all  on  1^  inch.     Others,  0  retained  on  2.5  inch; 

nearly  all  on  0.1  inch.     For  voids,  see  table,  below. 

Gravel.    Clean  quartz,  passing  a  IHnch  mesh,  2  per  cent,  passing  a  No. 

10  mesh.     Voids,  29  per  cent. 

Water.     With  Portland  cement,  0.09  cu.  ft.  (  =  5.7  Ibs.)  per  cu.  ft.  of 

rammed  concrete;  with  natural  cement,  0.12  cu.  ft.  (  =  7.5  Ibs.). 
For  Results,  see  p  1146. 


1146 


CONCRETE. 


For  Directory  to  Experiments,  see  pp  1135-9. 

Crushing  Strength  of  12  in.  Concrete  Cubes,  in  Ibs.  per  sq.  in. 

Experiments  by  A.  W.  Dow,  as  above: 
Parts  by  volume;  cement,  1;  sand,  2;  aggregate,  6. 


Aggregate 

Voids  in  Aggregate. 

Crushing  Strength, 
Ibs.  per  sq.  in.,  after 

No. 

0 

1 

p__ 

Mortar, 

J<§ 

1 

i  er 
Cent, 
of  Vol. 

in 
percentage 
of  Voids. 

10 
Days. 

45 
Days. 

3 
Mos. 

6 
Mos. 

1 

Year. 

s 

2 

pp 

o 

•a     7 

6 

45.3 

83.9 

908 

1790 

2260 

2510 

3060 

3    8 

3 

3 

35.5 

107.0 

950 

1850 

2070 

2750 

*     9 

4 

2 

37.8 

100.6 

2840 

1  10 

6 

39.5 

96.2 

2700 

6 

29.3 

129.1 

694 

1630 

2680 

1840 

2820 

^  12 

6 

45.7 

83.9 

1630 

1530 

1850 

1 

6 

45.3 

83.9 

228 

539 

375 

795 

915 

•3    2 

3 

3 

35.5 

107.0 

108 

364 

593 

632 

841 

S     3 

4 

2 

37.8 

100.6 

_ 

915 

I     4 

6 

39.5 

96.2 

800 

6 

29.3 

129.1 

87 

42'l 

361 

344 

763 

15     6 

6 

45.7 

83.9 

596 

829 

15     

15.  Tests  of  Metals,  '98,  p  572. 

15  a.  Cinder  Cone  with  Port  cem;  ult  comp  strength. 

Specimens;  12-inch  cubes;  water  10  to  \21A  Ibs  per  cu  ft  of  cone. 
Results : 


Proportions  by  volume: 


Cement  Sand 
1 
1 
2 
2 
2 
2 
2 
2 
3 
3 


Cinders 
3 
3 
3 
3 
4 
4 
5 
5 
6 
6 


No.  of  tests    Lbs/sq  inch 


90 
39 
102 
38 
98 

30-38 
90-99 
29 
91 

16 


1541 
2053 
1098 
1634 

904 
1325 

724 
1094 

529 

788 


16.  Considerc,  Genie  Civil,  '99. 
16  a.  Ductility. 
Specimens  and  results ; 

Cone  cantilevers,  1:3,  6  cm  sq,  60  cm  long,  tension  side  reinfd  by  3 
round  iron  bars  4J4  mm  diam. 

Treatment.  Loading  such  that  bendg  mom  was  the  same  for  all 
cross  sees.  In  one  of  the  prisms,  load  increased  until  unit  stretch  =  0.002. 
Then  loads,  =  44  to  71  %  of  this  original  load,  were  applied  139,000  times; 
stress  returning  to  0  each  time. 

Results.  Unit  stretches,  0.000545  to  0.00125;  strgth  but  little 
reduced.  Similar  tests  of  unreinfd  specimens  gave  unit  stretch,  at  rupture, 
only  0.0001  to  0.0002;  the  reinforcement  apparently  enabling  the  cone  to 
endure  far  greater  deformation  than  when  not  reinfd.  But  see  Expts  36,  38. 


EXPERIMENT   AND   PRACTICE.  1147 

For  abbreviations,  symbols  ami  references,  see  p  947 1. 

17     

17.  €.  E.  Fowler,  A  S  C  E,  Trans,  '99,  Vol  42,  p  117. 
17  a.  Results.     Proportions,  assuming  that 

1  bbl  Portland  cem      =   3.8  cu  ft. 

34  cu  yds  concrete          =   abt  27  cu  yds  after  ramming. 
Those  cones,  for  which  the  vols  of  stone  appear  in  bold-face  type  (as  l.OO), 
have  their  voids  filled  or  more  than  filled;  while,  in  those  printed  in  plain 
type  (as  1.04),  the  voids  are  not  filled  and  the  cone  is  porous  and  deficient 
in  strgth.  • 

Quantities  in  1  cu.  yard  of  concrete: 

Stone  with        Stone  with 

Cement,  Sand,  40  %  voids,       50  %  voids, 

Proportions  Barrels  cu  yds  cu  yds  cu  yds 


1  :2 
1  :2 
1  :  2 
1  :3 
1  :3 
1  :3 
1  :  4 
1  :4 
1  :4 


3  1.77  0.51  O.87  1.05 

4  1.59  0.47  O.95  1.15 

5  1.39  0.42  1.04  1.26 

4  1.30  0.57  O.83  l.OO 

5  1.16  0.52  O.92  1.11 

6  1.04  0.48  l.OO  1.20 

6  1.00  0.55  0.91  1.09 

7  0.92  0.51  O.97  1.17 

8  0.83  0.47  1.03  •         1.25 


The  foregoing  figures  agreed  well  with  the  results  of  practice.  The  column 
for  stone  with  40  %  voids  closely  represents  broken  limestone,  which  breaks 
into  pieces  of  various  sizes;  while  the  column  with  50  %  voids  represents 
trap  rock,  which  breaks  into  pieces  of  more  nearly  uniform  size. 

18     

18.  Tests  of  Metals,  '99. 

18a.  €ompressive  Strength  Of  12"  cubes  of  dry  Portland  ce- 
ment   concrete,  for  Geo.  A.  Kimball,  Chief  Engr   Boston  El  Ry  Co. 
Specimens ; 

Sand.  Coarse,  clean,  sharp.  Voids,  measd  loose  and  moist,  33  %; 
measd  after  settling  by  saturation  with  water,  25  %. 

Stone.    Conglomerate  from  Roxbury,  Mass.    Voids,  measd  loose,  49.5  %. 

4.8  %  passed  2  y/  ring,  caught  on  2"  ring  ; 
76.7  %       "        2"         "    ,        •'  1"     "   ; 

18      %       "        1"         "    ,        "  W     "   ; 

0.5  %      "      W 

Treatment.  Mixt  by  hand.  Water  barely  showed  after  ramming. 
Cubes,  except  those  tested  at  7  days,  buried  in  wet  ground  until  within 
one  wk  of  testing.  In  general,  5  cubes  of  each  mix  of  each  brand  were 
tested  at  each  of  the  ages. 

Results.  Ultimate  eompressive  strengths,  Ibs/D".  Each  max  or  min 
is  the  mean  of  five  or  more  tests,  upon  cubes  made  from  one  of  the  four 
brands  of  cem,  and  thus  refers  to  the  cem  giving  max  or  min  strgth  under 
the  stated  conditions.  The  avs  are  those  of  such  results  for  the  4  brands. 

Age                   1:2:4  1:3:6  1  :  6  :  12 

max        av        min  max       av         min  max       av      min 

7  ds      2219     1525       904  1550     1232       892  759       583     417 

1  mo     2642     2440     2269  2174     2063     1816  1218     1042     873 

3  mos  3123     2944     2608  2538     2432     2349  1257     1066     844 

6  mos  4411     3904     3612  3170     2969     2750  1583     1313     815 

For  formulas,  deduced  from  these  results  by  E.  Thacher,  see 

II  35,  p  1106. 

j«j     ____ 

19.  W.  A.  Rogers,  Chic,  Mil  and  St  P  Ry,  Westn  Soc  Engrs,  Jour,  1899 » 
Jun,  Vol  4,  No.  3,  p  262,  R  R  Gaz,  '00,  June  15,  p  402,  July  27,  p  514. 

19  a.  Effect  of  cold,  and  of  mixing  with  salt  water.  Specimens ; 
comp  strength  of  12-inch  cubes  of  Port  and  nat  cem  cone.  8  cubea 

76 


1148 


CONCRETE. 


For  Directory  to  Experiments,  see  pp  1135-9, 


Atlas  Port,  1  cem,  3  gravel  (2  sand,  1  pebbles),  4  hard  crusher  run  lime- 
stone; 8  cubes  Louisv  nat,  1  cem,  2  gravel,  3  stone. 

Same  as  used  in  track  elevation  masonry  by  Chic,  Mil  and  St  P  Ry. 

Treatment.  All  the  cubes  made  by  same  person  in  molds  of  1" 
lumber,  and  left  in  molds  until  broken. 

Results. 


Portland 


Natural 


Temp,  F 

Ibs/sq  in. 

Temp,  F 

*lbs/sq  in 

I  cube  in  warm  office  28  days 
1       "     "       "          "     28     '' 

80°  to     18° 

>1290t 
>1290t 

85°  to     40° 

300 
defective 

1       "  outdoors*           28     " 

57°  to  —24° 

902| 

57°  to  —10° 

200 

1       "            "                  28     " 

" 

690| 

" 

256 

1       "            "                  28     " 

in  office              28     ' 

85°  to     32° 

>1290t 

85°  to     40° 

376 

1       "  outdoors*           28     ' 

57°  to  —24° 

57°  to—  10° 

in  office              28     ' 

85°  to     32°   >1290f 

85°  to     40° 

352 

1       "   outdoors  *  **    28     " 

57°  to  —  24°  ,  >1290t 

57°  to  —10° 

237 

1       "                               28     " 

>1290t 

247 

19  b.  Character  of  aggregate ;  comp  strength. 
Specimens.      12"  cubes  of  Port  cem,  gravel  and  stone.     Gravel,  2/3 
coarse,  sharp  sand,  1  /3  pebbles  from  sand  to  1 J^".     Each  result  the  average 
of  3  cubes.     Age  28  days. 

Results.  Ibs/sq  in 

1:3:  4.5       hard  crusher-run  limestone 1270 

1:3:  4.5       soft  screened  " 1170 

1  :  3  :  4.5       washed  gravel  %  to  2  in 1050 

1:4:7          soft  screened  limestone ' 714 

1  :  4  :  3^5  }    washed  gravel  H  to  2  in  j 642 

19  c.  I>irt  in  sand  and  aggregate ;  comp  strength. 
Specimens.     "Dirty"  sand  and  gravel  contained  apparently  abt  10% 
dirt     whictf  had  the  appearance  of  containing  a  large  amount  of  iron." 


Results. 


With  sand,  tensile, 
90  days,  Ibs/Q" 


Clean 457 

Dirty 627 

Dirtier 515 


1  :2 
492 
541 
514 


1  :3 
349 
430 
396 

•     20 


With  gravel,  comp,  12"  cubes, 

28  days,  Ibs/Cf 

1:2:5  1  :  2.5  :  5 

1097  838 

988  928 

1020 


20.  Edwin  Thacher,  E  N,  '99,  Sep  21. 

20  a.  "Several  brands  of  Port  cem  were  improved,  in  tensile  strength, 
by  a  delay  of  from  1  to  4  hrs  betw  mixing  and  laying."  Ransome. 

21     

21.  <5eo.  W.  Rafter,  A  S  C  E,  Trans,  Dec  '99,  Vol  42,  p  104. 

21  a.  Volume ;  consistency,  richness  and  proportion  of  mortar. 
Specimens :  544  12"  cubes,  broken  on  the  U.  S.  Govt  testing  machine 

at  Watertown,  Mass.     Port  cem;  sand,  86.5  to  93.5  Ibs/cu  ft;  agg,  broken 
stone.     Cubes  abt  2  years  old. 

"Dry,"  only  a  little  more  moist  than  damp  earth; 

"Plastic,"  ordinary  consistency  used  by  masons; 

"Excess,"  under  moderate  ramming  the  cone  quaked  like  liver. 

*  During  the  first  part  of  the  28  days,  temp  fell  to  —10°  and  —20°  F  ; 
afterward,  thawing  during  day,  freezing  at  night. 

t  Flaked  slightly.     Strgths  exceeded  capacity  (185,000  Ibs)  of  machine 

j  Cold  believed  to  have  retarded  setting. 

**  Mixed  with  salt  water,  1  pint  salt  to  10  qts  water. 


EXPERIMENT   AND    PRACTICE. 


1149 


For  abbreviations,  symbols  and  references,  see  p  947 1. 

S    =  vol  of  sand      in  mortar  to  1  vol  cem; 
M   =      "     "  mortar  "  cone       "   1     "      " 
A    =      '      "  agg        "       "          "   1     ' 
C    =      '      "  cone  made  with         1     ' 
Results. 


Volume 


! 

Mortar   =   33  %  agg 

Mortar   =   40  %  agg 

1 

Proportions 

Shrkg 

Proportions 

Shrkg 

0 

O 

S 

M 

A 

C 

t 

8 

M 

A 

C 

t 

D. 

1 

1.57 

4.74 

4.30 

9.3 

1 

1.64 

4.10 

3.82 

6.8 

P. 

1 

1.83 

5.51 

5.01 

9.1 

1 

1.66 

4.14 

3.82 

7.7 

E. 

1 

1.70 

5.11 

4.64 

9.2 

1 

1.70 

4.24 

3.97 

6.4 

D. 

2 

2.42 

7.29 

6.74 

7.4 

2 

2.44 

6.12 

5.89 

3.8 

P. 

2 

2.45 

7.28 

6.62 

9.1 

2 

2.50 

6.28 

5.83 

7.2 

E. 

2 

2.35 

7.02 

6.36 

9.4 

2 

2.60 

6.47 

5.97 

7.7 

D. 

3 

3.15 

9.49 

8.78 

7.5 

3 

3.21 

8.03 

7.36 

8.4 

P. 

3 

3.30 

9.92 

8.89 

10.4 

3 

3.31 

8.23 

7.62 

7.4 

E. 

3 

3.25 

9.72 

8.83 

92 

3 

3.43 

8.57 

7.90 

7.8 

D. 

4 

4.18 

12.69 

11.75 

7.4 

4 

4.24 

10.71 

9.84 

8.1 

P. 

4 

4.28 

12.94 

11.66 

9.0 

4 

4.35 

10.96 

10.09 

7.9 

E. 

4 

4.37 

13.14 

11.78 

10.4 

4 

4.33 

10.84 

9.64 

11.1 

D. 

5 

5.04 

15.05 

14.29 

5.1 

5 

4.42 

11.25 

P. 

5 

5.00 

15.00 

13.66 

9.1 

5 

5.00 

12.50 

lV.56 

V.5 

E. 

5 

5.08 

15.20 

13.6.0 

10.5 

5 

5.24 

12.90 

21  b.  Density  of  concrete ;  thoro  ramming, 

Vol  of  1  :  1  mortar,        Vol  of  rammed  cone,  approx, 


0.33  X  vol  of  agg, 
0.40  X     "    "    " 


0.91  X  vol  of  agg, 
0.93  X     "    "     " 


21  c.  Density    of   aggregate;    compacting. 

2"  ring,  and  having  43.3 


_        Portage    stone, 

broken  to  pass  a  2"  ring,  and  having  43.3  %  voids  when  slightly  shaken  in 
the  measure,  had  9nly  37.4  %  voids,  as  a  mean  of  5  trials,  after  being  packed 
in  the  measure  with  a  tamping  iron,  used  about  as  forcibly  as  in  ordinary 
ramming  of  cone. 

22     

22.  Tests  of  Metals,  '00,  pp  1109,  &c.     For  Contractors  Plant  Co. 
22  a.  Specimens;    Port   cem,   sand,   crushed   stone,    1:3:5.     Stone 
passed  thru  a  2  Yi'  ring;  pieces  passing  a  Yz    ring  screened  out. 

A,  hand-mixt;     B    and    €    mixt    in    a    portable    gravity 
mixer  8  ft  long,  consisting  of  a  steel  trough  containing  numerous  rows  of 
steel  pins,  staggered.     Water  from  a  spray  pipe  strikes  the  mixer    about 
midway  its  length.     Hence  cone  is  mixt  dry  in  the  upper  half,  and   wet  in 
the  lower. 

Stone  spread  evenly  on  a  platform  in  front  of  mixer 
Sand  '     top  of  stone 

Cem  "    sand. 

Material  then  shoveled  into  mixer. 

B.  Allowed  to    form  a  cone-shaped  pile,  stones    accumulating    around 


All,  2  days  in  air,  2 


Material,  as  discharged,  levelled  off  with  hoe. 
12"  cubes;  beams  from  4"  X  6"  to  6"  X  6"  30"  span, 
mos  in  water,  1  mo  in  air. 


*  Consistency  :  D  =  dry  ;  P 
100  (A  — C) 
t  Shrinkage  =    - 


plastic  ;  E  =  excess. 


1150  CONCRETE. 

For  Directory  to  Experiments,  see  pp  1135-9. 

Results ;  Cubes  Beams 

Comp  strength,  Ibs/D"  Rupture  modulus.  lbs/G" 

max           av            min  max  av  min 

A           3516         3187         2930  454  414  367 

B           4451         4256         4041  564  525  450 

C            4380         4123         4019  536  451  348 

2jj     

23.  W.  H.  Ileiiby.  Jour  Assoc  Eng  Socs,  Sept  1900,  p  153. 

23  a.  Cinder  Concrete  loses  from  M  to  %  of  its  strength  by  being 
thoroly  wet;  but  fully  regains  its  strgth  upon  being  dried. 

g^     

24.  E.  Dnryea,  Jr,  "Cement,"  Vol  2,  '01       See  E.  Thacher,  in  A  S 
C  E,  Trans,  '05,  Vol  54,  Part  E,  p  447. 

24  a.  Finish. 

Tunnel  portals,  Los  Angeles,  Cal.,  two  coats,  1  cem  :  4  sand  :  1  lime  paste. 
Showed  hair  cracks  where  finished  smooth. 

Pedestals,  Chicag9  &  E  111  RR,  1  cem  :  1  sand.     In  good  condition. 

Piers,  Arkansas  River  bridge,  Kan  City  So  R  R.,  two  coats,  1  cem  :  3  sand, 
one  coat,  1  cem  :  1  sand.  In  good  condition. 

1  cem  :  3  sand  :  1  lime  paste,  considered  best.  Excessive  troweling 
should  be  avoided.  Finish  should  be  kept  damp  for  two  weeks. 

25     

25.  Thayer  School  expts,  '02.     J.  B.  Mclntyre  and  A.  L.  True. 

25  a.  Permeability.     97  expts,  specimens  10"  diam,  9"  high,    %" 
pipe  inserted  4".     Pressures,  20,  40  and  80  Ibs/Q"  (46,  92  and  185  ft  heads), 
2  hours.     All  specimens  with  from  30  to  45  %   1:1  mortar  were  imper- 
meable.    Some  with  40  to  45  %  of  1  :  2,  and  some  with  1:2:4  and  1  :  2.5  :  4, 
were  impermeable  under  80  Ibs.      1  :  2  :  4  or  1  :  2.5  :  4  recommended  for 
moderate  pressures. 

26     

26.  Bretiill4,  "Experiences  sur  le  Ciment  Arme,"  Ann  des  Fonts  et 
Chaussees,  '02,  p  181. 

26  a.  Corrosion  and  adhesion  in  water. 

Specimens;  4  slabs  36"  X  39,"  11.8"  thick;  respectively  1320,  1320, 
1760,  2200  Ibs  Port  cem,  11.6  cu  ft  sand,  31.8  cu  ft  pebbles,  %"  to  1"  diam. 
Rods  %o"  diam,  placed  at  diff  dists  from  the  surfs  of  the  slabs. 

Treatment;  slabs  placed  in  water  under  heads  of  40  to  50  ft  (17  to 
22  Ibs/Q")  which  were  transmitted  undiminished  to  the  centers  of  the 
blocks.  Pressures  relieved  from  time  to  time.  Treatment  maintained  for 
several  days.  Slabs  then  left  in  air,  exposed  to  weather. 

Results.  The  metal  was  found  perfectly  preserved;  but  its  surf,  which 
was  bright  when  placed,  was  found  dull  when  exposed  after  the  expt,  and 
adhesion  was  destroyed  where  the  water  had  circulated. 

26  b.  I^uster.     Bars,  with  bright  surf,  placed  in  cem  mortar  for  several 
days,  showed  dull  surf  after  removal  of  the  mortar,  indicating  chemical  action 
betw  the  cem  and  the  iron.     It  is  probably  by  such  action  that  rust  is  re- 
moved from  rusted  bars,  placed  in  cem  mortar      The  iron  salt,  formed  by 
this  action,  is  dissolved  by  the  water  which  penetrates  to  the  iron  surface. 

26  c.  Gain  and  loss  of  weight.  Small  pieces  of  sheet  iron, 
placed  in  cem  mortar,  gained  about  0.01  %  in  wt  in  76  days.  Subsequently 
placed  in  running  water,  such  plates  lost  wt,  indicating  the  solubility  of  the 
compound,  the  formation  of  which  had  increased  the  wt. 

26  d.  Time;  adhesion.  Iron  plates,  35  X  70  X  5  mm  (1%  X 
2%  X  0.2  ins)  were  laid  upon  freshly  laid  cone,  in  which  the  mortar  (500 
kg  Port  cem  to  1  cu  meter  sand)  flushed  to  the  surf.  At  diff  periods,  these 
plates  showed  av  adhesion  as  follows: 

27  12  17  23  27  days 
0.278         0.636           0.946            1.132            1.295            1.316            kg/sq  cm 
3.96           9.01            13.5              16.1              18.4              18.7               Ibs/sq  inch 

The  results  of  Expt  26  d  were  not  materially  modified  when  the  mortar 
was  kept  in  the  sun,  or  mixt  warm  or  very  wet. 


EXPERIMENT   AND   PRACTICE.  1151 

For  abbreviations,  symbols  and  references,  see  p  947 1. 

27    

27.  G.  Y.  Skeels,  Asst  City  Engr,  Sioux  City,  Iowa.   E  N,  '02,  Nov  6, 
p382. 

27  a.  Avs  of  2  and  4  briquets,  1  day  in  air,  14  ds  in  water.     Port  cem. 
Under  continuous  mixing  for  8  or  10  hrs,  neat  cem  mortar  lost  about 

%  of  its  tensile  strength  ;  1  :  2  lost  about  %. 

28     

28.  Thos.  S.  Clark,  Resident  Engr  in  Chg  of  Construction  of  Man- 
hattan R  R  Power  Station,  New  York.     E  N,  '02,  Jul  24,  p  68. 

28  a.  Retempering;    strength.      Neat   nat    cem  mortar    mixed 
initially  with  28  %  water;  sand  nat  cem  mortar  with  14  %.     Retempered 
an  hour  after  mixing,   "enough  water  being  added,  as  in  practice,  to  bring 
the  mass  back  to  its  original  consistency."     One  day  specimens  3  hours 
in  air,   the  others  24  hours.     Retempered  specimens   showed,  in  general, 
about  half  the  normal  strgth. 

Similar  results  were  obtained  when  the  cem  was  moistened  every  15 
mins  during  the  hour.  In  such  cases,  in  practice,  the  strgth  is  sometimes 
increased  by  adding  a  little  fresh  cem. 

Port  cem  mortars,  retempered  after  standing  an  hour,  failed  to  show 
marked  deterioration,  probably  because  Port  cem  sets  more  slowly  than 
nat  cem. 

29     

29.  W.  Purves  Taylor,  A  S  T  M,  Vol  3,  p  376,  '03. 

29  a.  Age ;  soundness.  Ageing  of  finely  ground  cem  permits  hydra- 
tion  of  the  free  lime,  nearly  always  present,  rendering  it  inert  and  preventing 
expansive  action.     Specimens,  made  with  cem  one  wk  old,  were  unsound; 
but,  as  the  age  of  the  cem  increased ,  the  soundness  of  the  specimens  improved 
until,  when  the  cem  was  5  wks  old,  the  specimens  were  sound. 

29  b.  Fineness;  soundness.    The  larger  particles  of  coarsely  ground 
cem  are  not  readily  hydrated.     A  cem,  of  which  33  %  remained  on  a  No  200 
sieve  and  13  %  on  No  100,  checked  and  cracked  in  the  boiling  test;    but 
became  sound  when  reground  until  all  passed  the  No  100  sieve  and  allowed 
to  season  for  2  weeks. 

30     

30.  French  Government   Commission,  Beton  und  Eisen,  '03, 
Vol  5. 

30  a.  Ductility.       Cone     1:2:4.     Results    similar     to    Considered 
(see  Expt  16  a).     Ductility  greater  when  hardened  in  water  than  when 
hardened  in  air. 

31     

31.  Chas.  List,  Assn  Eng  Socs,  Jour,  Mar,  '03,  Vol  30,  No.  3,  p  128. 

31  a.     Effect  of  sea  water  at  Gautemala,  Central  America. 

Hollow  piles,  in  sea  water,  filled  with  cone  in  which  sea  water  had  been 
used  for  mixing.  Some  of  the  mortar  leaked  out,  and  formed,  with  the' 
surrounding  sand,  masses  of  cone  which  adhered  to  the  piles.  When  piles 
were  removed,  cone  was  found  perfectly  hard  and  adhering  tenaciously  to 
the  piles. 

31  b.  Railway  bridge  foundation,  built  1895.  Lean  cone  mixt  with 
and  standing  in  brackish  water.  Of  excellent  quality  in  '03. 

31  c.  Regrinding.     Cem  brought  from  Hamburg,  Germany,  in  bbls. 
Vessel  sprang  a  leak;  cem  considered  a  loss,   and  value  refunded.     Cem 
stored  under  the  floor  of  a  warehouse  with  open  sides  and  exposed  to  mois- 
ture of  ground  and  to  spray  from  sea.     Cem  caked  hard  enough  to  be  used 
as  foundations  for  wooden 'posts  in  buildings.     This  caked  cem  was  broken 
as  fine  as  possible,  and  mixt  with  sharp  beach  sand  and  brackish  water. 
Cone  perfectly  hard  in  3  days  and  used  in  bridge  foundations  in  brackish 
water. 

32     

32.  Geo.  W.  L,ee,  Jr.,  E  N,  '03,  Mar  19,  p  246. 
Finish. 

32  a.  New  York  Central  R  R.     Forms  (2"  tongued  and  grooved  pine) 
coated  with  soft  soap  ;  openings  in  joints  filled  with  hard  soap.     Cone 
deposited  and  drawn  back  from  mold  with  a  square-pointed  shovel,  and  1  :  2 


1152  CONCRETE. 

For  Directory  to  Experiments,  see  pp  1135-9. 

mortar  poured  in  along  the  molds.  After  removal  of  molds,  and  while 
cone  green,  surf  rubbeoT,  with  a  circular  motion,  with  pieces  of  white  fire- 
brick, or  bricks,  of  1  cem  :  1  sand;  surface  then  dampened  and  painted 
with  1  :  1  grout,  rubbed  in  and  finished  with  wooden  float. 


33.  Wm.  B.  Fuller,  A  S  C  E,  Trans,  '03,  Jun,  Vol  50,  p  454. 

33  a.  Reinforced  Concrete  tank  at  filter  plant,  Little  Falls,  N.  J. 
10  ft  diam,  43  ft  high;  walls  15"  thick  at  bottom,  10"  at  top;  built  in  8 
hours;  all  cone  placed  from  top,  thus  falling  43  ft  at  first.     Mixt  very  wet; 
placed  5  cu  ft  (wheel-barrow-load)  at  a  time,  and  merely  joggled  into  posi- 
tion.    Tight  against  both  inflow  and  outflow;  intended  inside  plastering 
omitted  as  unnecessary.     Surfs  smooth,  no  stones  or  voids  showing. 

34 

34.  Prof.  C.  E.  Sherman,  E  N,  '03,  Nov  19,  p  443. 

34  a.  Clay  and  loam ;  Strength. 

Dyckerhoff  (German)  and  Lehigh  (American)  Port  cems,  with  sands 
containing  from  0  to  15  %  of  clay  and  loam.  Strgth  in  general  in- 
creased materially  with  the  percentage  of  clay  and  loam.  With  10  and  15 
%,  the  strgth,  at  12  mos,  was  from  15  to  50  %  greater  than  with  clean  sand. 

35     

35.  Tests  of  Metals,  '04,  pp  345-387. 

35  a.  Concrete  columns,  plain  and  reinforced;  ultimate 
comp  strength,  s,  Ibs/sq  inch  and  elastic  modulus,  E,*  Ibs/sq  inch. 

Specimens.  Port  cem  and  sand;  agg,  pebbles  and  broken  trap,  Y^  to 
1  /^  and  cinders.  Cols  approx  123^"  X  12  W  X  8  ft.  Reinforcing  rods; 
"Tw,"  %"  twisted;  "Cr,"  5/8*  corrugated;  "Th,"  %"  Thacher. 


No. 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 
11 
12 
13 
14 
15 
16 
17 
18 
19 


suits. 

Atrp 

Reinforcement 

f.  — 

Age 

—  *  . 

No.  & 

Mix           Agg 

Waterf 

mos  days 

Kind 

%  t 

s 

0.001  E* 

1  :  1  :  2     Pebbles 

42.5 

8 

0 

4Tw 

1.46 

2890 

2660 

7 

28 

None 

None 

1720 

2500 

1:2:3 

7 

28 

4Tw 

1.44 

2010 

2273 

53.1 

7 

25 

None 

None 

1769 

2155 

1:2:4 

56.7 

3 

13 

4  Tw 

1.43 

1990 

1938 

3 

16 

4Cr 

0.97 

2180 

2212 

•  « 

3 

14 

4Th 

1.03 

1990 

2315 

•• 

3 

15 

8  Tw 

2.86 

3160 

2500 

" 

3 

14 

8O 

1.94 

2830 

3049 

" 

3 

12 

8Th 

2.09 

2760 

3086 

" 

7 

26 

4Tw 

1.45 

1820 

2381 

" 

3 

17 

None 

None 

1710 

2358 

Trap 

"wet" 

5 

10 

None 

None 

1750 

2809 

Cinder 

•• 

5 

16 

4Tw 

1.45 

2095 

1404 

" 

5 

16 

None 

None 

871 

1000 

1  :  i 

:  6     Pebbles 

74.4 

7 

24 

4Tw 

1.44 

1370 

1036 

7 

None 

None 

462 

1442 

Trap 

5 

10 

8Cr 

1.94 

2290 

3086 

57.6 

0 

7 

None 

None 

471 

2208 

36.  F.  E.  Turneaure,  A  S  T  M,  Trans,  '04,  p  504. 

36  a.  Ductility.  Reinfd  cone  beams.  Unit  stretch  of  cone,  on  first 
appearance  of  cracking,  0.00010  to  0.00035,  made  up  of  sum  of  many  small 
cracks,  appearing  when  stress  in  steel  >  5000  lbs/O".  Plain  beams  rup- 
tured (without  preliminary  cracking)  with  equal  unit  elongation.  The 

*E  taken  betw  limits  of  comp  stress  as  follows,  Ibs/D":  Nos  15  and  17, 
100  to  600;  16,  600  to  1000;  19,  100  to  471;  all  others,  1000  to  1500. 

J%  of  cross  sec  area 


EXPERIMENT   AND   PRACTICE. 


1153 


For  abbreviations,  symbols  and  references,  see  p  947 1. 

cracks,  corresponding  to  the  lowest  unit  stretches,  were  invisible  on  dry 
cone,  but  were  detected,  in  moist  cone,  by  the  appearance  of  narrow  wet 
streaks  about  %"  wide.  A  little  later,  they  showed  as  dark,  hair-like  cracks. 

37     

37.  Prof  Bauschinger,  "Beton  und  Eisen,"  '04,  Vol  IV,  p  193. 
37  a.  Corrosion :  adhesion. 

Fragments  of  reinfd  cone  plates,  broken,  in  testing,  '87;  exposed 
outdoors  until  examined  in  '92.  Adhesion;  cone  broken  off  by  hammer 
blows,  breaking  only  in  immediate  vicinity  of  blows.  Corrosion;  steel 
rust-free,  even  close  to  the  exposed  surfs  of  fracture. 

37  b.  Tank,  injured  by  rough  treatment;  cracked;  reinfmt  laid 
bare  in  places.  Rust  only  where  so  exposed.  Adhesion  as  in  37  (a). 

37  c.  Fragments  of  Monier  plates  6  to  8  cm  thick.     Exposed,  at  inter- 
vals for  about  4  yrs,  to  sewage-polluted  water.     Cone  remained  hard; 
reinfmt  rust-free  1  cm  from  exposed  surface  ;  adhesion  excellent. 

38     

38.  A.  Kleinlogel.  Beton  und  Eisen,  '04,  'Vol  2. 

38  a.   Ductility.   Reinfd  cone    beams    15    X    30  cm,   220  cm    long. 
1:1:2,  cem,  sand,  limestone  screenings.     Kept  under  moist  sand  6  mos. 
Bendg  mom   constant   thruout   measd   portion.     Unit   stretches  in   cone; 
reinfd,  0.000148  to  0.000196;  plain,  0.000143. 


39.  Clarence  Coleman  ;  Report,  CM  of  Engrs,  USA,  '04.     Part  IV. 
Universal  Port  cem  made  from  blast  furnace  slag. 

Av  tensile  strgth,  Ibs/H" 
Sand*  Mix   WaterJJ     7          28       6       1     3 


39  a. 

Q 

§ 

Q 
Q 

S 

s 

S 

s 

s 
s 

s 
s 

stt 
stt 

1:3 

1:3 
1:3 

1:3 
1:3 
1:10 
1:10 

1:10 

1:10 

1:3 
1:3 

1:10 
1:10 

1:3 

1:3 

12.5 

12.5 
12.5 

12.5 
12.5 
Random 
Random 

Random 

Random 

8.25 
9.25 

Random 
Random 

8.25 
8.25 

da 

176 

173 
199 

1.00  t 

1.17f 
134 
253 

262 

222 

254 
244 

164 
184 

183 
183 

da 

298 

260 
274 

1.00  t 
1.09  t 
211 
274 

366 

388 

289 
317 

275 
314 

259 

272 

mo 
424 

411 
424 

yr 

yr 

Cem  exposed  in  sacks  to  ciamp- 

Caked  hard.  Not  set.    Regrouncl 
39  b. 
Cem  as  received  on  works  
Cem  after  4  to  10  mos  in  sacks  in 

39  c. 

Cone  haiid-mixt  on  platform  t 
Cone  mixt   in    cubical   bateli- 
mixeriS  .'  

324 
385 

420 

415 

380 
398 

446 
458 

361 
392 

343 
391 

462 

643 

399 
437 

445 
464 

340 
359 

394 
834 

39  d. 
As  in  laborat'y,  24  hours  in 
damp   closet,   then    immersed 

As  on  work,  10  days  under 
damp  cloth,  then  in  air  until 

39  e. 

8.25  %  water**  
9  25  %  water  ** 

39  f. 
I'ebbles  Vie  to  34  inch 

Pebbles  %  to  %  inch  
99  g. 

Sand  with  small  %  clay  

*  Q  =    Standard  crystal  quartz. 

S    =   Superior  Entry  sand;  passingsieve No.  4        10      20      30     50 

%  100    72.3  46.1  26.5    5.1 

t  Relative  strgths.  t  Briquets  made  of  cone  taken  from  the  works. 

§  A  batch  of  very  perfectly  mixt  cone  in  80  sees. 

1[  Cone  taken  from  mixing  platform      Stones  larger  than  %"  removed. 
**  In  order  to  approx  working  conditions,  the  mortar  was  allowed  to  stand 
30  mins  longer  than  under  ordinary  treatment. 

ttPassing  No  10  sieve.  tt  Water  in  percentage  of  dry  agg 

C9 


1154  CONCRETE 

For  Directory  to  Experiments,  see  pp  1135-9. 

4O     

40.  Prof  <  has.  L,.  Norton,  EN,  '02,  Oct  23,  '04,  Jan  14. 
Corrosion.     Several  hundred  briquets  of  various  mixes  and  consist- 
encies, with  steel  imbedded,  subjected  to  air,  steam  and  carbonic  acid. 

4O  a.  Steel  clean  when  imbedded.     3  wks  exposure. 
Steel  perfectly  protected  by  neat  cem  in  all  cases,  and  where  the  mortar 
was  mixt  wet,  so  as  to  cover  the  steel  with  thin  grout. 

In  cone,  rust  found  only  where  voids  or  other  defects  existed. 

40  b.  Steel  rusted  when   imbedded.     1    to    3    mos    exposure. 
Changes,  in  size  of  steel,  occurred  only  where  cone  had  been  poorly  applied. 

41     

41.  John  S.  Sewell,  on  Baltimore  fire,  E  N,  '04,  Mar  24. 

41  a.    Results.       "Concrete   undergoes    more   or   less    molecular 
change  in  fire;  subject  to  some  spalliiig.    Molecular  change  very  slow. 
Calcined  material  does  not  spall  off  oadly  except  at  exposed  square  corners. 
Efficiency,  on  the  whole,  is  high.     Preferable  to  commercial  hollow  tiles 
for  both  floor  arches  or  slabs,  and  col  and  girder  coverings." 

41  b.  Reinfd  cone  cols,  beams,  girders,  and  floor  slabs,  at  least  as  de- 
sirable as  steel  work  protected  with  the  best  commercial  hollow  tiles. 

41  c.  *'  Stone  cone  spalls  worse  than  any  other  kind,  because  the  pieces 
of  stone  contain  air  and  moisture  cavities,  and  the  contents  of  these  rup- 
ture the  stone,  when  hot.  Gravel  is  stone  that  has  had  most  of  these 
cavities  eliminated  by  splitting  through  them,  during  long  ages  of  exposure 
to  the  weather.  It  is  therefore  better  than  stone  for  fire-resisting  cone." 

41  d.  "  Broken  bricks,  broken  slag,  ashes  and  clinker  all 
make  good  fire-resisting  cone." 

41  e.  *'  Cinders,  containing  much  partly  burned  coal,  are  unsafe,  be- 
cause these  particles  actually  burn  out  and  weaken  the  cone.     Locomotive 
cinders  kill  the  cem,  besides    being  combustible.     Cinder  concrete  is  safe 
only  when  subjected  to    the  most  rigid  and  intelligent  supervision;  when 
made  properly,  of  proper  materials,  however,  it  is  doubtful  whether  even 
brickwork  is  much  superior  to  it  in  fire-resisting  qualities,  and  nothing  is 
superior  to  it  in  lightness,  other  things  being  equal." 

42     

42.  Kinile  Low,    A  S  C  E,  Trans,  June  '04,  Vol  52,  p.  96.     Buffalo 
Breakwater. 

42  a.  Shrinkage. 

Cement 258  cu  yds 

Sand 365 

Pebbles 1175 

Broken  Stone 972 

Total  Materials.  .  .  2770 

Blocks  made 2054 

Shrinkage 716         "      =  25.8  % 

•     43     - 

43.  Alex.  B.  Moncrieff,    Engr   in    Chief,    South    Australian    Govt 
Letter  to  authors,  June  7,  '04. 

43  a.  Permeability. 

Specimens.  Cone  blocks,  2  ft  cubes  (8  cu  ft),  for  expts  in  connection 
with  construction  of  Barossa  dam.  Ingredients  same  as  used  on  dam. 
Agg  %"  to  2",  with  varying  voids.  Preparation  of  aggs  very  carefully 
watcned. 

Treatment.  Water  brought  to  cen  of  block  in  Yj'  wrought  iron  pipe 
terminating  in  a  T  piece,  wrapped  with  hemp  which  formed  a  bulb  abt 
4"  diam. 

Results.  All  the  blocks  became  practically  tight.  Cone 
used  in  dam  ' '  was  based  upon  the  results  of  the  expts  principally  with  blocks 


EXPERIMENT   AND   PRACTICE.  1155 

For  abbreviations,  symbols  and  references,  see  p  9472. 

Nos  7  and  8."     There  is  "practically  nothing  that  could  be  called  a  leak" 

thru  the  dam.* 

Q   =  vol  of  mixing  water,  %  of  volume  of  cone; 

._  vol  of  mortar  —  vol  of  voids 
X  =  excess  mortar  =  100  -  vol  of  voida  ~> 

A   =  age  of  block,  in  weeks,  when  subjected  to  pres; 

/     =  interval  in  mins,  betw  application  of  pres  and  appearance  of  water 

on  surf  of  block; 

Head  =  100  ft  =  43.4  Ibs/Q."     Under  200  ft  (86.8  Ibs/Q")  "the  effect 
closely  resembled  the  results  obtained  from  the  head  of  100  ft." 

Observed  Leakage* 


No. 

Cem.  Sand 

Agg 

* 

X         A 
%  Weeks 

I 
Mins. 

Mean  rate 
Pints      U.  S  gals  /mo 

1 

1        1.84 

5.26 

16.65 

5 

11 

t 

t 

t 

2 

1        1.84 

5.26 

15.45 

5 

11 

34 

% 

in    7  wks. 

0.065 

3 

1        1.50 

4.63 

16.04 

5 

10 

18 

Vso 

•  •    4    " 

0.005 

4 

1       2.00 

4.50 

16.04 

15 

10 

14 

14 

"     2    " 

4.000 

5 

1       1.75 

4.13 

16.65 

15 

9 

12 

27 

"    7    " 

2.353 

6 

1        1.50 

4.12 

16.04 

10 

8 

35 

y50 

"    2    " 

0.006 

7 

1        1.50 

3.90 

14.26 

12.5 

6 

28 

% 

"    2    " 

0.037 

8 

1       1.50 

3.70 

13.68 

15 

5 

30 

Ho 

"     2    " 

0.006 

44      : 

44.  Edwin  Thacher,  A  S  C  E,  Trans,  '05,  Vol  54,  pp  425,  &c. 

44  a.  Effect  of  cold.  Jlelaii  arch  bridge,  at  Mishawaka,  Ind, 
3  spans,  110  ft  each,  built  in  temps  ranging  from  0°  to  55°  F.  Hot  water 
admitted  to  mixer.  Cone  laid  at  blood  heat;  warm  enough  to  melt  snow 
48  hours  later.  Center  arch  completed  with  temp  about  25°  F.  The  next 
day,  temp  fell  to  0°  F.  Two  wks  later,  an  ice  jam  carried  out  the  centering 
and  left  the  a  roll  unsupported.  No  bad  effects  observed;  settlement 
but  little  greater  than  with  the  other  arches,  centering  under  which  was 
removed  later  and  in  the  usual  way. 

44  b.  Finish. 

Bridge  at  Oconomowoc,  Wis.  Mortar  face,  1  cem  :  1  granite  screenings 
:  1  torpedo  sand.  On  the  second  day  after  completion,  molds  removed  and 
surf  rubbed  with  a  soft  stone  and  water. 

Inman  arch,  Hohenzollern.  1  cem  :  5  broken  limestone.  After  setting 
12  hrs,  the  loose  cem  was  removed  by  water  and  brushes. 

Pacific  Borax  Co's  factory,  Bayonne,  N.  J.  Finished  to  represent  coursed 
ashlar,  by  inserting  wooden  strips  in  the  molds  and  dressing  the  faces  with 
a  pneumatic  hammer.  One  man  could  dress  from  300  to  600  sq  ft  in  10 
hours  by  machine,  100  to  200  by  hand.  Good  effect. 

"Mr.  Cummings  produced  a  good  finish  by  going  over  the  surf  with  a 
wire  brush  while  the  cem  was  still  green." 

Utica  &  Mohawk  Valley  Ry  viaduct,  Herkimer,  N.  Y.,  and  viaduct  over 
rys  at  Jacksonville,  Fla.  "A  very  superior  finish."  For  a  hard  wall,  wet 
the  surface  and  apply  a  thin  1  :  2  mortar  with  a  brush.  Rub  surface  with 
a  piece  of  grindstone  or  carborundum,  removing  board  marks,  filling  pores 
and  producing  a  lather  on  the  surf.  Go  over  this  lather,  before  it  dries, 
with  a  brush  dipped  in  water. 

For  a  green  wall  (molds  removed  in  less  than  7  days,)  use  a  thin  grout  of 
neat  cem,  instead  of  the  1  :  2  mortar.  Remainder  of  process  as  above. 

Use  smooth  molds,  deposit  wet  cone  directly  against  them.  After  re- 
moving molds,  float  the  surf  with  a  wooden  float,  using  only  sufficient 
mortar  to  fill  the  pores  and  give  a  smooth  finish. 

44  c.  Corrosion. 

Chicago.  Iron  rods,  in  limestone  cone  slabs  which  had  covered  sidewalk 
vaults  for  8  or  10  yrs,  rust-free.  E.  L.  Ransome. 

*  See  H  4,  p  1103.  t  Unreliable. 


1156  CONCRETE. 

For  Directory  to  Experiments,  see  pp  1135-9. 

Obelisk,  Central  Park,  New  York,  small  piece  of  iron  set  in  mortar  taken 
from  the  base.  Bright  after  2300  yrs.  Iron  drift  bolts,  from  bed  of  cone 
at  a  lighthouse  in  the  Straits  of  Mackinac,  rust-free  20  years  after  laying, 
Wm.  Sooy  Smith. 

Osage  River  bridge,  Mo.,  Iron  cyl  piers  filled  with  Louisv  cem  limestone 
cone.  Iron  absolutely  free  from  rust  after  7  yrs  service.  Albert  A.  Tro- 
con,  E  R,  Vol  38,  p  273. 

Steel  rods,  sheet  steel  and  expanded  metal,  embedded  in  cone  blocks 
3"  X  3"  X  8",  and  unprotected  steel,  all  enclosed  in  tin  boxes,  and  exposed, 
for  3  wks,  one  portion  to  steam,  air  and  carbon  dioxide,  one  to  air  and 
steam,  one  to  air  and  carbon  dioxide,  and  one  to  atmosphere  of  testing  room 

Conclusions : 

Cone  must  be  dense,  and  be  mixt  wet.     Neat  cement  a  perfect  protection. 

With  cinder  cone,  corrosion  due  mainly  to  iron  oxide,  not  to  sulfur. 

Cinder  cone,  if  dense  and  well  rammed,  about  as  good  as  stone  cone. 

Steel  must  be  clear  when  imbedded. 

Steel  must  be  coated  with  cem  before  being  imbedded.  Otherwise  there 
will  be  more  rust  than  steel  in  the  result.  Prof.  Chas.  L.  Norton,  Rep  No. 
2,  Ins.  Engng  Expt  Sta.,  Boston. 

Grenoble,  France.  Reinfd  cone  water  main,  Monier,  12"  diam,  1  %o" 
thick,  steel  framework  of  ^  and  Vie"  steel  rods.  15  yrs  in  damp  ground. 
Adhesion  perfect.  Metal  absolutely  free  from  rust. 

Berlin.  Reinfd  cone  retaining  wall.  After  11  yrs  use,  metal  found  free 
from  corrosion,  "except  in  some  cases  where  the  rods  were  within  0.3  or 
0.4"  from  the  surf."  Effect  of  the  cone,  in  preserving  metal,  not  due  to  the 
exclusion  of  air.  "Even  thq  the  cone  be  porous  and  not  in  contact  with 
the  metal  at  all  points,  it  will  still  filter  out  and  neutralize  the  carbonic 
acid  and  prevent  corrosion."  S.  B.  Newberry,  E  N,  Vol  47,  '02,  Apr  24,  p  335. 

Links  from  anchorage  of  a  suspension  bridge  partly  built  by  Roebling 
in  '55.  Removed  '75.  Perfect.  G.  Bouscaren,  E  R,  Vol  38,  p  253. 

Niagara  suspension  bridge  anchorage.  No  rust  where  limestone  was  not 
in  contact  with  metal  and  where  no  movement  had  taken  place.  Perfect 
after  25  yrs.  L.  L.  Buck. 

45    

45.  Wm.  B.  Fuller,  A  Treatise  on  Concrete,  by  T  and  T,  '05. 
45  a.  Moisture ;  effect  of  tamping : 

Moisture Dry  6  %      Saturated 

Reduction  of  vol,  %,  by  tamping 9.6  18.8  8.8 

Max  volume  in  sands,  when  water  is  betwn  5  %  and  8  %  by  wt. 

45  b.  Voids,  between  spheres  of  uniform  diam  ("large  masses  of 
equal  sized  marbles")  could  not  be  reduced,  by  pouring  and  tamping  into 
a  vessel,  to  less  than  44  %  of  the  mass.     See  f  30,  p  947  b. 

46    

46.  National  Fire  Protection  Assn,  Rept  of  Comm,  '05. 

46  a.  Fire  tests. 

Specimens.     Beams  8"  X  1 1  M"  X  6  ft,  each  with  3  plain  round  steel 
rods,  6  ft  6"  long,  imbedded  1",  2"  and  3"  from  bottom  of  beam.     Port  cem, 
Aggregates  Mixtures  Voids,  % 

Screened  coarse  gravel 1:  2:3,     1:  2.5  :  5,      1:  3.5  :  7  35 

Limestone,  <  1M"  "  42 

Screened  red  granite,  <  1  H" "  40 

Ordinary  cinders 1:2:5,      1:2:6  ....  .... 

Wet  mix.     Specimens  45  to  48  days  old. 

Treatment.     3  hours^n  furnace;  temps  1900°  to  2000°  F. 

Results. 

46  b.  Conductivity  was  lowest  in  the  cinder  concrete  and  in  the 
richer  cones.  Otherwise  materials  had  no  important  effect. 

46  c.  Strength  of  rods  impaired  25  %  at  770°  F.  Av  time 
reqd  to  reach  770°;  1"  imbedment,  1  h;  2",  2  hs;  3",  2.5  hs. 


EXPERIMENT   AND   PRACTICE.  1157 

For  abbreviations,  symbols  and  references,  see  p  947 1. 


46  d.  Clone  did  not  break  or  ehip  under  fire;  but  lost  practi- 
cally all  strgth  to  a  depth  of  4"  from  sides  and  bottom,  and  softened  per- 
ceptibly thruout.  The  cem  and  most  of  the  stone  were  thoroly  calcined  at 
surf,  and,  to  a  diminishing  extent,  to  a  depth  of  4".  In  all  cases,  a  little 
water  appeared  in  cracks  running  across  the  beams,  especially  with 
the  richest  mixtures  and  with  temp  at  212°  F. 

46  e.  Recommendations.     Materials    should    be    well    mixt,  wet, 
by  machine,  and  well  tamped.     Imbedment  should  be  <  2";  in  important 
cases,  3". 

47    

47.  John  H.  Quinton,  U.  S.  Geol  Surv,  "  Expts  on  Steel-cone  Pipes 
on  a  Working  Scale,"  U.  S.  Water-Supply  and  Irrigation  Paper  143,  '05. 

47  a.  Permeability.     To  determine  availability  of  such  pipes  under 
pres,  for  U.  S.  Reclamation  Service. 

Specimens.  Seven  reinforced  hand-mixed  cone  pipes,  5  ft  diam,  6* 
thick,  20  ft  long;  each  made  in  one  section;  one,  same  dimensions,  in  4 
sees.  Skilled  workmen.  In  3  of  the  7  pipes,  and  in  3  of  the  4  sees  of  the 
8th  pipe,  lime  was  used  in  the  mixture. 

The  pipes  varied  greatly  in  texture.  One  of  them  "seemed  to  be  of  a 
crumbly  nature,  and  it  would  have  been  easy  to  cut  a  hole  through  it." 
Another  was  "exceedingly  hard." 

Treatment.  The  pipes  were  tested  with  and  without  inside  linings  of 
cem  and  sand,  etc,  with  and  without  lime  paste.  The  Sylvester  soap-and- 
alum  wash  (p  928),  P  and  B  waterproof  paint,  and  other  paints  were  tried; 
and  clay  was  stirred  up  in  the  water  within  the  pipes.  Pressures  up  to 
70  Ibs/Q"  =  161.5  ft.  head. 

Results. 

47  b.  In  spite  of  all  precautions,  the  pipes  leaked,  especially  along  tamping 
seams,  leakage  decreased  greatly  under  pres,  as  percolating 
water  filled  the  pores  with  laitance;  but  in  the  mean  time  the  leakage  may 
be  sufficient  to  damage  foundations  of  pipe. 

47  c.  Dry  mixtures  gave  the  more  permeable  cone. 

47  d.  With  carefully  graded  gravels,  it  was  found  difficult  to  secure 
uniform  distribution  of  the  din  sizes. 

47  e.  Keep  cone  shaded  while  mixing  and  placing. 

47  f.  Interruptions  to  work  are  least  dangerous  with  wet  mixtures, 
in  tamping,  avoid  displacement  of  reinforcement. 

47  g.  Make  reinforcemt  strong  enough  to  protect  cone  against  ten- 
sile stress. 

47  h.  Soap  and  alum  mixture  of  advantage  in  making  cone;  but 
%"  plaster  found  advisable  on  inside,  in  two  coats,  the  first  with  lime  paste, 
to  retard  setting;  the  second  (applied  when  the  first  is  dry)  to  be  troweled 
smooth.  When  dry,  apply  thick  neat  cem  wash. 

47  i.  Reinfd  cone  pipes  not  recommended  for  heads  over  70  ft  (30  Ibs 
/Q'').  For  short  dists,  special  precautions  may  justify  100  ft  (43  Ibs/Q"). 

47  k.  Cone  pipes  liable  to  crack,  especially  along  tamping  seams; 
but,  even  if  cracked,  probably  drier  and  more  durable  than  other  kinds. 

47  1.  When  the  pipes  were  broken  up,  rust  appeared  upon  only  1  rod, 
which  was  rusted  all  around  for  a  length  of  about  1 J^",  where  a  large  and 
long-continued  leak  had  occurred.  The  pipe  had  been  lined  with  a  mortar 
containing  sal  ammoniac  (ammonium  chloride)  and  iron  filings. 


48.  Considere.     Beton  und  Eisen,  '05,  Vol  3 

48  a.  Ductility. 

Specimens.  Mixture,  400  kg  Port  cem,  0.4  cu  m  sand,  0.8  cu  m  lime- 
stone screenings.  Beams  15  X  20  cm,  3  m  long.  Tension  side  reinfd  with 
2  iron  bars  16  mm  round,  and  3,  12  mm  rd.  Bendg  mom  constant  thruout 
measd  length. 

Treatment.     One  beam  kept  in  water,  one  under  damp  sand,    6  moa. 


1158  CONCRETE. 

For  Directory  to  Experiments,  see  pp  1135-9. 

Results.     Max  unit  stretches 

kept  under  water 0.00107 

damp  sand 0.00050 

No  cracks  discovered,  altho  the  surf  was  smoothed  with  cem. 
Strength  unaffected. 

49    

49.  It.  Feret,  "A  Treatise  on  Concrete,  Plain  and  Reinforced,"  by 
Taylor  and  Thompson,  '05. 

49  a.  The  injurious  action  of  sea  water  is  due  chiefly  to  the  siilfuric 

acid  of  the  dissolved  sulfates;  hence,  the  cem  should  contain  as  little 
gypsum  (lime  sulfate)  as  possible.  Port  cem  should  be  low  in  aluminum 
and  in  lime.  The  presence  of  puzzolanic  material  is  advantageous.  The 
jonc  should  be  dense  and  impervious. 

50    

50.  Prof  Ira  H.  Woolsoii,   Report   to  Astoria   Light,   Heat   and 
Power  Co.,  '05. 

50  a.  Character;  strength. 

Strengths  in  Ibs/D" 


Tensile  Compressive 

Port  Cem,  1:2:4. 


Max       Av       Min  Max       Av      Min 

Sand  &  broken  limestone 176       161       153  2000     1753     1441 

Crushed*  &  broken  limestone  282       194       138  3400     2449     2040 

50  b.  Sand  contained  <  1  %  loam;  all  past  >£"  sieve;  75  %  past  20 
mesh  sieve.     Hudson  R  bluestone  (limestone)  passing  1  M"  screen,  retained 
on  %"  screen.     Cone  tampt  wet  in  molds,  1  or  2  days  in  air,  5  or  6  in  water. 
Air  dried  4  to  7  wks.     Results,  see  50  a. 

51    

51.  Prof  R.  C.  Carpenter,   Cornell   Univ,   Sibley   Jour   of   Eng*g, 
Jan,  '05. 

51  a.  Retardation  of  setting ;    gypsum    (lime  sulfate)    CaSO4, 
and    calcium    chloride,   CaCl2.     Both   ground   dry  with   the   clinker. 
Initial  set;  paste  bears  a  rod  Via  inch  diam,  loaded  with  M  lb. 

Final  set;        V34     "         "  "     1  lb. 

Time,  in  both  cases,  reckoned  from  time  of  mixing,  and  given  in  mins. 

Results.  Percentage  by  weightf 

0.0     0.5    1.0    1.5   2.0   2.5   3.0   3.5  4.0  5.0   6.0  7.0 
Time  in  minutes 

Initial  CaSO4 2         6...     80     24     29     30     2728     27     1918 

CaCl2 2     115  160  167  127  103     45     97   ..     73     68   .. 

Final  CaSO4  52       87   ...    157  114     79     69     72  45     59     37  59 

'     CaCl2 52     274  272  234  212  180  182  185    ..    160  145  .. 

51  b.  E.  Candlot  (Ciments  et  Chaux  Hydrauliques)  found  that  concen- 
trated solutions  of  CaClo  (such  as  100  to  400  grams  per  liter)  accele- 
rated setting  and  hardening. 

51  c.  Addition  of  slaked  lime  to  a  cem  containing  gypsum  which, 
with  time,  has  lost  its  retarding  effect. 

Initial,  mins  Final,  mins 

2  %  gypsum,  no  lime 12  15 

"       "      +  5  %  "  120  300 

2  to  5  %  of  lime  is  useful  in  this  respect,  but  not  without  the  gypsum. 
The  lime  does  not  diminish  the  strgth. 

52    

52.  Jas.  C.   Ilaiii.  Chic,  Mil  and  St  P  Ry.     E  N,  '04/Apr  28,  p  413 
E  R,  '05,  Jan  28,  p  103.     Sand;  size  and  cleanliness. 

*%"  crusher  screenings;  87  %  past  H"  sieve,  40  %  past  %"  sieve- 
t  1  %  =  about  4  Ibs  CaCl2  to  a  barrel  of  Port  cem. 


EXPERIMENT   AND   PRACTICE.  1159 

For  abbreviations,  symbols  and  references,  see  p  947 1, 

Specimens. 

52  a.  Impure  sands. 

1  :  3  Port  cem  mortars,  made  with 

(a)  sand  of  smooth  rounded  quartz  grains,  mixt  with  larger  fragments 
of  limestone  shells,  92  %  past  No  24  sieve,  28  %  past  No  50; 

(b)  "St  Paul  standd  sand,"  54  %  past  No  24;  11  %  past  No  50; 

(c)  "Ottawa  standd  sand." 

Results : 

Relative  tensile  strgths  (a)  100;  (b)  137;  (c)  107.5. 

Sand  (a)  made  excellent  cone  in  a  draw-span  center  pier. 

1  :  3  Port  cem  mortars,  with  sand  containing  3.2  to  15  %  clay;  strgths 
<  with  clean  sand.  With  nat  cem  1  :  3,  and  Port  1  :  2,  the  results  were 
generally  favorable  to  the  cleaner  sand. 

Sand  with  6  %  clay  gave  stronger  mortars  before  than  after  washing. 

Sands,  to  which  2  to  20  %  rich  loam  had  been  artificially  added,  gave 
mortar  testing  somewhat  irregularly  but  in  general  higher  than  those  with 
clean  sand. 

52  b.  Fine  sand,  with  clay.     A  sand,  all  passing  No.   100  sieve, 
93.2  %  passing  No.  200  (therefore  finer  than  most  cem.     See  Specfs),  and 
containing  12  %  clay,  gave  a  1  :  3  Port  cem  mortar  showing,  at  6  mos 
and  1  yr,  nearly  the  same  tensile  strgth  as  similar  mortar  made  with  "Ot- 
tawa standard  sand,"  but  the  mortar  was  weaker  at  shorter  periods. 

53     

53.  Jas.  C.  Haiti,  Engr  of  Masonry  Constn,  Chic,  Mil  and  St  P  Ry, 

E  N,  '05,  Mar  16. 

Oil.     Tests  by  Oeo.  J.  Oriesenauer. 

53  a.  A  neat  Port  cem  briquet.  2  yrs  old,  exposed  to  occasional 
drippings  of  signal  oil,  began  to  disintegrate  in  10  mos;  but  no  recent  cone 
structures  were  found  perceptibly  injured  by  oil.     A  cone  floor,  upon 
which  lubricating  and  lighting  oils  had  been  stored  for  6  yrs,  was  apparently 
unaffected.     Oil   penetrated   about  Ha".     A  piece  of   this  floor,  in  oil   10 
mos,  still  sound. 

53  b.  Port  cem;  neat;  1:3  sand;  1:3  limestone  screengs;  18  bri- 
quets each;  4  days  in  air.  Then  saturated  daily  with  signal  oil;  later 
less  frequently.  Cracks  appeared  in  the  1  :3  specimens  in  2J^  mos;  in 
neat  specimens  in  5  mos.  All  the  briquets  disintegrated  eventually. 

53  c.  Port  cem  ;  54  briquets,  neat;  36  briquets  1  :  3  sand.  7  d  in 
air.  Then  saturated  daily  with  oil;  later,  less  frequently.  Oils  used; 
extract  lard,  whale,  castor,  boiled  linseed,  crude  petroleum,  signal.  Cems 
made  from  limestone  and  clay,  marl  and  clay,  limest  and  slag.  Lard  oil 
disintegrated  most  of  the  briquets  in  from  2  wks  to  2y%  mos,  but  some  re- 
mained sound  for  9  mos.  Signal  oil  (animal  and  mineral  mixt)  had  nearly 
the  same  effect.  Whale  and  castor  oil  affected  only  a  few  briquets;  while 
petroleum  and  boiled  linseed  disintegrated  no  briquets.  Petroleum  di- 
minished strgth  somewhat.  Boiled  linseed  formed  a  protective  coating 
and  did  not  affect  strgth.  As  a  rule,  the  neat  briquets  yielded  first.  In 
general,  briquets  of  limestone  and  slag  yielded  most;  those  of  limestone 
and  clay  least. 

53d.  Silica  cem;  neat,  1:1,  1:2,  1:3,  sand.  1  briquet  each. 
2  yrs  in  water;  20  days  in  warm  air.  Signal  oil  2  yrs.  First  3  briquets 
sound;  1  briquet  (1:3)  disintegrating. 

53  e.  Linseed  oil,  Sylvester's  process  (p  928),  paraffine,  and  water  glass 
(soda  silicate)  were  applied,  as  coatings,  to  the  briquets,  but  all  failed 
to  protect  them  against  the  action  of  the  oils. 

53  f.  Rich  cone,  well  made  of  good  materials  and  well  set  and  sea- 
soned, is  best  for  resisting  oil.     In  practice,  cone  structures  are  rarely, 
if  ever,  saturated  with  oil,  as  were  these  specimens. 

54     

54.  Chas.  A.  Matcham,  Nat  Builders'  Supply  Assn,  E  R,  '05,  Apl 
15,  p  435. 

54  a.  Corrosion. 


1160  CONCRETE. 

For  Directory  to  Experiments;  see  pp  1135-9. 

Specimens  and  treatment.  6-inch  cone  cubes,  3  yrs  old,  with  3* 
steel  cubes  embedded. 

Two  cubes,  with  mi  painted  3"  steel  cubes  embedded,  exposed  to 
Bummer  and  winter  weather,  and  sometimes  covered  with  snow  ami  ice. 

Results. 

Steel  uninjured.  Crushing  strgths,  2920  Ibs  and  over  4166  Ibs/d*. 
One  6"  cube,  with  3"  steel  cube  (painted  with  metallic  paint)  embedded, 
placed  in  bottom  of  river.  Steel  uninjured.  Paint  disappeared. 
Crushing  strgth,  2907  Ibs/D". 

55     

55.  Prof  Ira  H.  Wool  HO  11.     E  N,  '05,  Jun  1. 

55  a.  Absorption. 

Specimens.  8"  cubes,  1:2:4,  3  weeks  old,  kiln  dried  13  days  at 
120°  F. 

Part  with  sand  with  <  1  %  loam;  all  past  0.125"  screen  ;  75  %  past 
20-mesh  sieve.  Part  with  %"  limestone  crusher  screenings;  87  %  past  M" 
screen;  40  %  past  0.125"  screen;  sand  and  dust,  enough  to  fill  voids.  Stone 
past  1  y?  ring. 

Results. 

Av  absorption ;  4  hours,  2.87  % ;  24  hrs,  2.95  % ;  48  hrs,  3.33  %.  No 
marked  diff  betw  sand  and  screenings. 

56     

56.  W.  C.  Hoad,  Univ  of  Kansas.     E  N,  '05,  Aug  10. 
<  lav  and  l-oani;  strength  and  absorption. 

56  a.  Port  cem  with  (a)  staodd  Ottawa  sand,  1  :  3;  (b)  2  to  20  %  of  the 
sand  replaced  by  clay  or  loam.     At  90  days,  relative  strgths;  in  general: 
(a)  100;  (b)  94  to  125. 

56  b.  Up  to  6  or  8  %  clay  or  loam,  there  was  no  increase  of  absorption, 
with  loam;  and  about  10  %  decrease,  with  clay.    With  higher  per- 
centages, the  absorption  increased  somewhat. 

57     

57.  Eng'  News,  '05,  Sep  28. 

57  a.  Permeability. 

Reinforced  concrete  cistern,  75,000  gals.  1:2:4,  Port  cem, 
river  sand,  gravel.  1"  layer  of  1  :  1  mortar  on  bottom.  Walls 
washed  with  3  coats  neat  cem  grout,  cream  consistency,  put  on  with 
whitewash  brush  after  walls  were  well  wetted.  Each  coat  dried  for  24  hrs. 
If  too  wet,  the  coating  crackt.  If  too  dry,  it  could  not  be  brusht  on.  For  a 
few  days  after  filling,  lost  %e"  in  depth  per  day.  Perfectly  tight  since. 
Cistern  built  with  outside  air  at  temp  below  2O°  F ;  but  was  covered 
with  boards,  and  two  coke  salamanders  were  used. 

58     

58.  Prof  Ira  H.  Woolson,  E  N,  '05,  Nov  2. 

58  a.  Flow. 

Specimens.  Cols,  4"  diam,  12"  long,  formed  in  steel  tubes,  1A"  to 
M"  thick,  and  allowed  to  set  and  remain  there  for  17  days,  when  the  cone 
appeared  very  hard.  Cone  remained  in  tubes  during  tests. 

Results.  Under  loads  of  150,000  Ibs,  the  cols  in  the  stouter  tubes  were 
merely  shortened  <  M";  but  under  loads  of  120,000  to  150,000  Ibs,  the 
cols,  in  some  of  the  lighter  tubes,  were  bent  out  of  shape  and  shortened  by 
3  }4",  their  diam  increasing  from  4"  to  about  5".  Upon  removal  of  the  tubes, 
the  cone  was  found  unbroken,  solid  and  perfect ! 

59     

59.  J.  Itt.  Braxton,   U.  S.  Asst  Engr.     Reports,  '05-6      E  N,  '08, 
May  14,  p  525. 

Corrosion  in  sea  water. 


EXPERIMENT   AND   PRACTICE. 


1161 


For  abbreviations,  symbols  and  references,  :-;ee  p  9472. 

59  a.  Yi'  steel  rods  imbedded  in  4  cone  blocks  made  with  coral  sand  and 
broken  brick.  2  blocks  in  4  ft  of  sea  water;  2  in  a  dry  closet,  both  for  more 
than  a  yr.  The  rod  in  one  of  the  dry  blocks  showed  signs  of  rusting.  The 
others  were  as  bright  and  smooth  as  when  placed. 

59  b.  30  blocks,   12"    X    12"    X    6";  Port  cem,    1:3:5,  broken  brick. 
Made  under  usual   working  conditions.     %"  twisted   steel    rod,  8"  long,  in 
cen  of  each  block.     20  blocks  with  coral  sand,   10  with  ordinary  quartz 
sand.     Half  of  each  placed  in  ocean,  half  in  air  without  roof.     Broken  after 
1  yr,  3  wks.     In  all  the  blocks  placed  in  the  ocean,  the  rods  were  found  in 
perfect  condition.     All  the  others  were  more  or  less  rusted. 

6O     

60.  Wm.  R.  Baldwin- Wiseman,  Instn  C  E  Procs,  '06,  Vol  163, 
p319. 

60  a.  Puddling-  effect  of  water  flowing  thru  cone  discs,  13"  diam,  6" 
thick,  1  :  4  Port  cem,  crushed  gravel  passing  1"  ring.     Sp  gr  of  cone  2.23, 
140  Ibs/cu  ft.     In  wooden  molds  10  wks.     Water,  for  pres,  pumped  from 
chalk  formation,  hardness  reduced  from  18°  to  6°.     Air  temp  12°  to  15°   C 
=  54°  to  59°  F.     Pressures,  24  to  60  Ibs/Q"  =  55  to  139  ft.     Leakage  as 
per  Fig  4.     Toward  the  close  of  the  expts,  small  stalactitic  growths 


100 

§'C0 

^ou 

1" 

20 

0 

\ 

\ 

^v, 

I 

--  — 

0 

—       - 

I 

0 

2 



0 

•  • 

i 

—  •  —  *- 
0        46 

Days 
Fig  4.     Puddling. 

formed  on  bottom  of  test  piece,  and  leakage  was  absorbed  by  evaporation. 
Near  the  surf,  the  water,  under  high  pres,  dissolved  out  some  of  the  material, 
but  deposited  it  in  the  pores  farther  on,  where  the  pres  had  been  reduced  by 
passage  thru  the  block. 

61     

61.  San  lord  E.  Thompson.     A  S  T  M,  Procs,  Vol  VI,  1906,  p  379. 
61  a.  Consistency ;    effect    upon     density,*    permeability 
and  compressive  strength. 

Density  and  permeability  specimens,  21  days  old;  comp  strgth  specimens 
5M  mos. 

Specimens. 

Atlas  Portland  cem;  Newburyport  sand,  sp  gr  =  2.65;  trap,  sp  gr  =  2.78. 
1  :  2.3  :  4.6  by  vol;  1  :  2  :  4  by  wt. 

Consistencies  used.  Water,  %  •} 

Dry.     Like  damp  earth;  water  glistened  on  surf  under  hard 

ramming 5.4 

Medium.     Looked  wet  when  mixed.  Did  not  flow  in  mixing 

box.     Slightly  quaking. ...    6.9 

Wet ....;..  .-••-.•:••      9-2 

Very  wret.  Like  thick  soup.  Settled  to  a  level  in  mixing 
box.  Required  scoop  shovels  for  handling.  Slightly  wet- 
ter than  usual  in  building  work 11.0 

Extremely  wet 13.7 

*  Density  =  vol  of  solid  particles  in  unit  vol  of  cone, 
t  Percentage  of  weight  of  cem,  sand  and  stone. 


1162 


CONCRETE. 


For  Directory  to  Experiments,  see  pp  1135-9. 


Results.     See  Fig  5. 

^  0.850 
«  0.800 
§  0.750 
Q  0.700 


2000 


e   Stren 


f! 

•|S 
-SJ4003  I 


Oo 


er 

m 


M  5.4  6.9  9.2  11.0 

Water,  Percentage  of  Dry  Materials  by*Weight. 

Fig  5.     Consistency. 


13.7 


For  a  given  consistency,  the  percentage  of  water  depends  upon  the 
nature  of  the  cem,  and  upon  the  size  and  dryness  of  the  sand  grains.  A  fine 
sand,  or  one  with  many  fine  grains,  may  require  twice  as  much  water  as 
coarse  sand  requires. 

61  b.  Elastic  iiio<luliiK.  Twelve  12"  cubes,  deformations  measd  in 
5"  gaged  length.  Averages  of  4  specimens,  1:2:4;  approx  1,  2,  6  and  17 
mos  old.  Dry,  4,450,000  lbs/D";  medium,  4,200,000;  very  wet,  3,000,000. 
No  appreciable  increase  of  modulus  with  age. 

61  c.  Age;  permeability.  Blocks  tested  at  21  and  84  days,  showed 
permeabilities  abt  as  2  :  1.  Pressure,  80  Ibs/sq  in  =  185  ft  of  water. 

61  d.  An  excess  of  water  washes  out  fine  cem,  forming  laitance, 
reducing  strgth  and  increasing  permeability.  Thickness  of  laitance 
formation,  Y%'  in  very  wet  mixtures. 

61  e.    Mr.  Thompson    concludes    that,    in   building    and    other 
reinfd  work,  the  cone  should  be  only  wet  enough  "to  flow  sluggishly  around 
and  thoroly  imbed  the  steel  and  permit  smooth  surfaces  against  the  forms," 
and  that  medium  or  quaking  cone  is  suitable  for  ordinary  mass  cone,  such 
as  foundations,  heavy  walls,  large  arches,  piers  and  abuts. 

62     

62.  A.  Black,  E  N,  '06,  Aug  30,  p  236. 

62  a.  Character  of  sand ;  strength  and  absorption. 
Specimens.  Passing  No 

170  sieve. 

A,  crushed  gneiss,  screened  thru  y>?  mesh 90.8  % 

B,  Cowe  Bay  sand,  much  used  in  and  about  New  York   .  .   95.8  % 

C,  fine  clean  silicious  sand 95.5  % 

Results.     In  7  and  28  days,  1  :  2  and  1  : 3  mortars,  A  and  B  gave,  in 

general,  from  20  to  50  %  greater  tensile  and  comp  strengths  than  C.    In 
general,  the  stronger  mortars  showed  the  higher  absorptions. 

63     

63.  Alex.  B.  Moncrieff,  E  N,  '06,  Aug  30,  p  227. 

63  a.  Briquets  in  water  2  yrs,  in  air  7  days  arid  in  oil  6  mos.    In  general, 
neat  cem  lost  from  0  to  36  %  strgth,  while  3  :  1  gained  from  0  to  65.5  %, 
by  air  drying  and  immersion  in  oil. 

63  b.  Briquets  in  air  7  days;  then  6  mos  in  either  oil  or  water.  The  neat 
cem  briquets  in  oil  were  from  0  to  55  %  weaker  than  the  neat  cem  in  water; 
the  3  :  1  briquets  in  oil  were  49  to  79  %  weaker  than  those  in  water. 


EXPERIMENT   AND   PRACTICE. 


1163 


For  abbreviations,  symbols  and  references,  see  p  947 1. 


63  c.  Briquets  in  water  9  wks;  others  in  water  4  wks,  in  air  1  wk  and  in 
oil  4  wks.     With  few  exceptions,  the  neat  cem  briquets  in  oil  were  from  abt 
0  to  40  %  stronger  than  like  briquets  in  water,  while  the  3  :  1  briquets  were 
from  abt  0  to  63  %  stronger  than  like  briquets  in  water.     Many  of  the  oil- 
treated  briquets  "snapped  like  flint." 

64     

64.  Prof  Arthur  ST.  Talbot,  Univ  of  111.  Bull,  Vol  IV  No.  1. 
'06,  Sept  1. 

64  a.  Adhesion  and  friction.     '04. 
Specimens  and  results. 

Mix,  1:3:6. 

Pull,  in  Ibs/D"  of  net  section; 

Elastic  limit,  in  Ibs/D"; 

Adhesion,  in  Ibs/Q"  of  imbedded  surf: 

Johnson  bars          Round  bars  Square  bars 

^2"  %"~*        H" W~^  %" 1A"  %"~* 

Pull 71,412  34,500  31,500  21,500  35,656  26,510  20,860 

Elaslim 60,000  58,300  42,500  40,500  45,000  33,300  35,000 

Adhesion 595  420          249  315  297  286  325 

With  all  the  Johnson  bars,  the  specimens  split  or  broke.  All  the 
plain  rods  slipped.  6  of  the  11  Johnson  bars,  and  4  of  the  11  bars  %" 
square,  were  "struck  6  quarter-swing  blows  with  a  10-lb  sledge,"  reducing 
their  adhesion  by  abt  5  to  20  %. 

Specimens. 

64  b.  '05-6.  Cylinders,  6"  diam,  6"  and  12"  long;  60  days  old.  Mixture 
of  Am  Port  cems,  tensile  strgth,  neat,  723  Ib/Q"  at  7  days;  1  :  3,  354  at  7 
ds,  533  at  75  ds;  coarse  mortar  sand;  broken  limestone,  screened  thru  1' 


and   over 


38,000;  Flat,    45,000;  Cold 
53,000. 
Results. 

No. 
of 
tests    Steel        Size 


Metal,   elas  lim,   Ibs/Q";    Mild  steel   (M),   Round. 
rolled   shafting    (C),  87,000;  Tool   steel     (T). 


Mix 


6         1\ 

1       1/3"  round 

1  :3 

5.5 

6 

" 

1  :  2 

4 

6 

%"  round 

1  :3 

5.5 

4 

" 

1  :  2 

4 

3 

%"  round 

1  :3 

5.5 

4 

" 

1  :  2 

4 

3 

%"  round 

1  :3 

5.5 

3 

" 

1  :  2 

4 

3 

'     i  m  x  %«" 

1  :3 

5.5 

3         < 

D      1"    round 

3 

W  round 

'• 

3 

T      %"  round 

1  :3 

6 

Imbedded 

length, *- 

ins.         Adhesion 


372 
412 
355 
465 
373 
404 
402 
414 
125 
136 
157 
147 


Lbs/Q"  im- 
bedded surface 


Friction      f/a 


12 


210 

227 

227 

297 

268 

266 

228 

223 

84 

67 

50 


0.57 
0.55 
0.64 
0.64 
0.72 
0.65 
0.57 
0.54 

0.67 
0.49 
0.32 


Rich  mixture  generally  superior.  Cold  rolled  shaftg  and  tool 
Steel  generally  inferior,  owing  to  uniformity  of  sec  and  smoothness  of  surf. 

65     

65.  Jos.  W.  Kl Ims.  Chemist,  Commissrs  of  Water  Works,  Cincinnati. 
E  R,  '06,  Oct  27,  p  487. 

65  a.  Permeability. 

Specimens.  Port  and  nat  (Louisville)  cem;  Ohio  River  quartz  sand, 
clean,  rather  fine,  quite  uniform  in  size;  limestone  screenings,  with  much 
very  fine  dust. 

«"  cubes; 

Port  cem;  (a)  1  cem  :  2  sand,  10  %  water;  (ft)  1  cem  :  1  sand  :  1  screen- 
ings, 11  %  water;  (c)  1  cem  :  2  screenings,  14  %  water. 

77 


1164  CONCRETE. 

For  Directory  to  Experiments,  see  pp  1135-9. 

Nat  cem;  (d)  1  cem  :  2  sand,  15  %  water;  (e)  1  cem  :  1  sand  :  1  screen- 
ings, 15  %  water;  (/)  1  cem  :  2  screenings,  17  %  water. 

Hollow  Cylinders;  6"  diam,  8"  long,  2"  hole;  Port  cem  and  sand, 
1  :  1,  10  %  water. 

Treatment.  Water  (clear)  brought  to  centers  of  specimens.  Cubes, 
1  day  in  air,  6  in  water.  Cyls,  1  d  in  air,  27  in  water,  4  in  air. 

Results.  Leakage  past  thru  mortar  1  W  to  2"  thick.  Cubes ;  under 
50  Ibs/D"  (115  ft  head)  maintained  from  3  to  16  hrs,  little  or  no  water 
(max  =  0.16  gal/hour  per  Q  ft)  past  thru  the  Port  cem  cubes;  from  0.29 
to  2.40  gals /hour /D  ft  thru  the  nat  cem  cubes.  Portland,  leakage  became 
appreciable  at  60  to  75  Ibs/Q"  (138  to  173  ft);  nat,  at  15  Ibs  (35  ft).  The 
1  :  2  sand  cubes  were  the  most  permeable.  Cylinders,  15  to  30  Ibs/D" 
(35  to  70  ft);  leakage  0.00023  to  1.228  gals/hour /Q  ft. 

Leakage  diminished  very  noticeably  with  time. 

66     

66.  W.  J.  Douglas,  Engr  in  Charge  of  Bridges  for  Wash,  D.  C.,  E  N,  '06, 
Dec  20,  p  649. 

66  a.  A  bridge,  painted  with   a  cement  rich   in  free   lime, 

showed  afterward  a  mass  of  blotches  of  different  colors. 

67     

67.  Prof  C.  von  Bach,  Zeitschrift  des  Vereins  Deutscher  Ingenieure, 
'95,  '97. 

67  a.  Relation    between    unit    stretch    and     unit    stress. 
"  Potenzgesetz  "  (Law  of  powers). 

Specimens.  Cone  cylinders,  25  cm  diam,  1  m  long.  Deformations 
measd  on  a  length  of  75  cm. 

Treatment.  Load  of  8  kg/sq  cm  alternately  applied  and  released  until 
the  deformation  no  longer  increased.  Then  similarly  with  16  kg/Q  cm, 
and  so  on  to  40  kg/Q  cm. 

Results.  From  the  beginning,  the  deformations  increased  faster  than 
the  loads.  Let 

s    =  unit  stress  =  stress  per  unit  of  cross-section  area; 

L   =  original  measd  length  of  75  cm; 

I     =  reduction  of  L  under  compression; 

e    =  l/L  =  unit  deformation; 

c    =  a  coefficient,  depending  upon  character  of  material; 

m  =  an  exponent, 

Then,  e  =  l/L  =  c  .  a™ 

Approximate  Values 

Mixture  1  /c 


Cem     Sand     Gravel     Stone         For  sin  kg/Q  cm.       For  sin  Ibs/Q".      m 
1          2.5  5  0  298,000  6,147,000  1.14 

1          2.5  0  5  457,000  9,940,000  1.16 

1          3.0  0  0  315,000  6,672,000  1.15 

1  1.5  0  0  356,000  6,781,000  1.11 

(1/c  for  «  in  Ibs/Q")  -H  (1/c  for  s  in  kg/Q  cm)  =  14.2234m. 

68     

68.  R.  C.  Carpenter.  A  S  T  M,  Procs,  '07,  Vol  7,  p  398.  Unseed 
and  engine  oil ;  soundness  and  tensile  strength.  Neat  cem 
briquets,  some  with  2  %  of  linseed  or  of  engine  oil  added  to  the  mixing 
water;  the  others  without  oil.  No.  of  briquets  not  stated. 

68  a.  Soundness.  24  hours  in  moist  air.  Briquets,  mixt  without 
oil,  S9und  after  8  days  in  either  oil.  Briquets  mixt  with  and  without  oil, 
remained  sound  after  boiling  for  3  hours. 


EXPERIMENT   AND   PRACTICE. 


1165 


For  abbreviations,  symbols  and  references,  see  p  947 1. 

68  b.  Tensile  strength. 

Oil  in  mix  Tensile  strength,  Ibs/Q" 

1  day  7  days  28  days 

None 430  696  743 

2  %  linseed 180  493  572 

2  %  engine 332  689  696 

69     

69.  M.  R.  Barnett,  Inst  C  E,  Procs,  '07,  Vol  167,  p  153. 

69  a.  Action  of  soft  water  upon  limestone  cone.     Thirlmere 
aqueduct,  water  supply  of   Manchester,  Eng.      Section  of    aqueduct,  made 
with  limestone  cone.     Floor,   9"   thick,   reduced   about    M"  in  thickness, 
honeycombed,  eaten  thru  in  many  places,  and  leaking  badly. 

69  b.  Samples  of  the  limestones,  from  which  the  cone  was  made,  were 
kept,  for  6  mos,  in  running  soft  water,  in  the  aqueduct,  and  were  found  to 
lose  wt  at  rates  ranging  from  6.8  to  18.1  %  per  year,  while  sample  blocks 
of  neat  and  1  :  1  Port  cem  mortar,  gained  5.5  and  3.6  %  respectively. 
Deg  of  hardness  of  water,  2.18. 

70     

70.  Prof  Ira  H.  \Voolson,  AS  T  M,  Procs,  '05,  p  335;  '07,  p  404. 
High  temperatures  and  thermal  conductivity. 

70  a.  Mixture,  1  :  2  :  4;  with  cinder,  1:2:5.     Cem,  an  equal  mix  of 
3  Portlands.     Sand,  sharp,  fair  qual,  "not  especially  clean";  90  %  past  a 
12-mesh  sieve.     Agg,  fair  quality  boiler  cinder,  with  most  of  the  fine  ashes 
removed;    %"   clean   quartz   gravel;  crusht   trap.     Mixt   moderately   wet; 
tampt  in  molds  until  water  flusht  to  surf. 


2,000 


1,000°  1,500° 

Temperature,  in  degrees  F. 
Fig  6.     Heat  Resistance. 


2,000 c 


2,500° 


7O  b.  High  temperatures.     '05,  p  335.     Fig  6. 

Specimens.  For  comp  strgth,  4"  cubes;  for  elasticity,  prisms  6"  X  6" 
X  14".  3  cubes  and  3  prisms  tested  without  heating;  3  cubes  and  2  prisms 
of  each  agg  (trap  and  limestone)  at  each  temp. 

Results. 

7O  c.  Elastic  modulus,  E.  For  E,  the  trap  and  limestone  curves 
nearly  coincided. 

7O  d.  After  heating  to  2000°  and  2250°  F,  the  limestone  cubes  appeared 
sound  while  hot,  but  disintegrated  when  cooled. 


1166 


CONCRETE. 


For  Directory  to  Experiments,  see  pp  1135-9. 


7O  e.  After  cooling  from  750°  F,  both  trap  and  limestone  prisms 
were  covered  with  minute  cracks.  Under  higher  temps,  these  cracks  in- 
creased in  number  and  in  size,  and  the  prisms  warped  and  disintegrated 
after  cooling  from  1500°  F. 

7O  f.  The  trap  and  cinder  cone  specimens  remained  sound,  while 
the  gravel  cone  specimens  cracked  and  crumbled  in  pieces,  probably 
owing  to  high  expansion  coeff  of  quartz,  and  to  the  fact  that  this  coeff 
in  one  direction,  is  double  that  in  the  perp  direction. 

Heated  Face    A5 


il 

!! 

|! 

! 

ILJ 

j 

5 

9    o    o    o    o    o    <j> 

*  —  3- 

->i                                 »*-- 

3—  > 

Fig1  7.     Thermal  Conductivity.     Dimensions  in  inches. 


1,400 


1,200 


fc-  1,000 


800 


•100 


200 


JL, 


0       10       20      30      40       50       60       70       80       90     100     110    120 
Time,  in  Minutes. 

Trap. 
Fig  8.     Thermal  Conductivity. 


70  g.  Thermal  conductivity,  '07,  p  404.     Figs  7  and  8. 

Specimens.  Cone  blocks,  with  holes  as  in  Fig  7.  Dimensions  in  inches. 
Thermo  couple  in  each  hole.  Mixture  as  in  7O  a. 

Treatment.  Specimens  in  molds  24  hrs,  in  water  48  hrs,  kept  moist 
2  or  3  wks,  allowed  to  dry  well.  Age,  at  test,  about  2  mos.  Blocks  placed 
in  furnace  doorway. 

Results.  Fig  8  shows,  for  one  of  the  trap  cone  specimens,  the  times, 
in  mins,  reqd  to  transmit  the  furnace  temps  thru  diff  thicknesses 
of  cone.  Each  curve  is  marked  with  this  thickness  in  ins.  Drop  of  curves, 
at  and  near  200°  F,  attributed  to  steam  generation. 


EXPERIMENT   AND   PRACTICE.  1167 

For  abbreviations,  symbols  and  references,  see  p  947 1. 

7O  h.  2  to    2  W  of    cone    (if    it  remains    in    place)  will    protect 

reinfg  metal  during  any  ordinary  conflagration. 

7O  i.  Exposed  reinforcing  metal  will  not  conduct  heat  injuri- 
ously to  imbedded  portion. 

7O.5.  Win.  B.  Fuller  and  Sanford  E.  Thompson,  "  The  Laws 
of  Proportioning  Concrete,"  A  S  C  E,  Trans,  '07/Dec,  Vol  59,  pp  139-143. 

Elastic  modulus,  E,  under  compression. 

Specimens.  6"  sq  cone  prisms,  18"  long  ;  age,  abt  140  ds.  Giant  Port 
cem.  Agg  :  Cowe  Bay  sand  (CS),  Jerome  Park  screenings  (JSc).  Agg  : 
Cowe  Bay  gravel  (CG),  Jerome  Park  stone  (JSt). 

Results. 

Effect  of  maximum  size  of  stone. 
Mix.  ..............  1  :  9*         1:3:6         1  :  2.81  :  5.62  1  :  2.92  :  5.88 

Stone  Elastic  modulus,  E,  in  millions  of  pounds  per  square  inch. 

2.25  ins 2.1  2.4  3.3  3.0 

1.00    "    1.7  1.8  3.1  2.6 

0.50    "    1.4  0.9  ...  -  2.2 

Effect  of  quantity  of  cement,  in  %  of  total  dry  material.* 
Elastic  modulus,  E,  in  millions  of  pounds  per  square  inch. 


Cem.. 
E.. 


With  JSc  and  JSt. 
8  10  12.5  15 
1.8  2.1  2.3  4.7 


With  CS  and  CG 
8.5    10.6    13.25    15.9 
2.3      3.9      3.7       4.3 


With  JSc  and  CG 

10.2    12.75    15.3 

3.5      3.8        3.5 


71     

71.  Richard  I,.  Humphrey,  U.  S.  G  S  Bull,  No.  324,  '07.     Report 
on  San  Francisco  fire  of  Apr  18,  '06. 

Results. 

71  a.  Cone  probably  the  best  material  for  fireproofing  cols.  Its 
stiffness  supports  the  steel  within,  softened  by  the  heat. 

71  b.  "Cone  proved  superior  to  brick  as  a  fireproofing  medium." 
71  c.  At  high  temps,  cone  loses  its  water  of  crystallization. 

71  d.  Cone,   especially   when   reinfd,  resisted   both  earthquake   and 
fire.     The  coiic  dam,  at  San  Mateo,  altho  within  a  few  hundred  yds  of 
the  fault,  was  uninjured.     Solid  cone  floors,  altho  of  very  poor  quality, 
proved   satisfactory      The  cinder  cone  used,   in  floors  and  elsewhere, 
was  high  in  sulfides,  and  injurious  to  reinfmt. 

72     

72.  Wm.  B.  Fuller,   NatI  Assn  of  Cem  Users,  Procs,  '07,  pp  95-7. 
Grading  and  proportions. 

72  a.  Tests  of  6  beams,  6"  square,  6  ft  long;   1  cem  to  8  of  sand  and  stone; 
rupture  moduli  in  Ibs/D":    1:2:6,  319;   1:3:5,  285;   1:4:4,  209; 
1:5:3,  151;  1:6:2,  102;   1  :  8  :  0,  41. 

72  b.   With  a  given  percentage  of  cem,  the  densest  mixture  of  sand 
and  agg  gives  the  strongest,  the  least  permeable  and  therefore  the  most 
durable  cone,  and  that  which  works  most  easily  and  therefore  best  fills  up 
voids  and  corners. 

73     

73.  Commission  du  ciment  arm€,  Paris,  '07. 

73  a.  Shrinkage  and  expansion.   Cone  shrinks  while  hardening 
in  air,  and  expands  under  water. 

*  Material,  larger  than  0.2"  diam  (abt  62  to  68  %  of  total)  graded  in 
accordance  with  the  recommendations  of  the  authors.  See  Plain  Concrete, 
11H  23  to  25,  p  1089. 


1168  CONCRETE. 

For  Directory  to  Experiments,  see  pp  1135-9, 

74     - 

74.  T.  1^.  C 'on (Iron,  of  Condron  and  Sinks  Co.,  representing  Expanded 
Metal  &  Corr  Bar  Co.  Jour,  Western  Soc  of  Engrs,  '07,  Feb,  Vol  12,  No.  1. 
Experiments  by  Prof  C.  E.  De  Puy,  Lewis  Inst.,  Chicago. 

74  a.  Adhesion ;  plain  and  deformed  bars. 

Specimens. 

Cone  cylinders,  6"  diam,  8",  12",  16",  20",  24"  long.  Hand  mixt,  accu- 
rately proportioned;  1:2:4,  Port  cem,  coarse  sand,  broken  limestone, 
W  and  under,  without  dust.  Fairly  wet,  so  as  to  enter  molds  easily  and  be 
churned  with  a  small  rod.  All  the  cone  mixt  in  one  batch.  The  8"  and  16" 
blocks  were  25  days  old  when  tested,  the  others  31  ds.  The  rods  past  en- 
tirely thru  the  blocks. 

Results.  Stress,  Ibs/D"  of  imbedded  surf 


Slip  >  0.01"  Slip  >  1/32" 

Diam         • • >  . • . 

in  Imbedded  Imbedded 

inches         12"  24"  12"  24" 

Adhesion,  Ibs/D" 

Round iVie  269  178  289  190 

Square K>Ae  316  229  341  242 

Twisted,  Buffalo "  334  291  357  306 

Twisted,  Ransome* "  324  332  366  350 

Johnson.f  New "  474  471  612  506 

Johnson,  Old* 12/16          651  535  786  535 

75     

75.  A.  A.  Knudson,  Am  Inst  Elec  Engrs,  Procs,  '07,  Feb,  Vol.  26, 
Part  I,  p  231;  E  N,  '07,  Mar  21,  p  328. 

75  a.  Electrolysis. 
Specimens. 

1  :  1  cem  and  sand,  Port  and  Rosendale.  Blocks  molded  in  metal  water 
pail;  positive  electrode,  a  short  2"  wrought  iron  pipe  in  axis  of  block,  im- 
mersed about  8". 

Treatment.  Blocks  placed  in  water  (one  in  fresh,  one  in  salt)  in  tank; 
negative  electrode,  a  piece  of  sheet  iron,  immersed  in  tank.  Current  0.1 
ampere. 

Results.  After  30  days,  Portland  blocks  (which  had  cracked 
under  current)  were  easily  broken,  and  showed  yellowish  deposits  (ap- 
parently iron  rust)  and  softened  cone,  in  the  seams.  Pipes  lost  more 
than  2  %  by  corrosion.  Final  electrical  resistance  =  10  X  initial 
resistance,  and  about  =  resistance  of  dry  cone.  Rosendale,  cracks  ap- 
peared in  6  days.  One  of  the  pipes  eaten  thru. 

76     

76.  J.  TL.  Van  Ornum,  A  S  C  E  Trans,  Vol.  51,  p  443,  '03/Dec,  and 
Vol  58,  p.  294,  '07/Jun. 

76  a.  Fatigue.     Neat  cem  blocks  in  comp.     Repeated  loadings  cause 
failure  if  the  load  is  >  abt  half  that  reqd  to  crush  with  one  application. 

Vol  58,  p  294. 

76  b.  Fatigue.     About  600  tests. 

Specimens. 

Blocks  5"  X  5",  12"  long,  in  cqmp,  and  beams,  4"  wide,  6"  deep,  6  ft  span, 
reinfd  by  2  plain  steel  bars,  W  in  square.  Each  batch  made  8  blocks  or  4 
beams.  Mix,  1  :  3  :  5  by  vol.  Standd  Am  Port  cem,  tested  by  A  S  C  E 
specifications  (p  942).  Sand  from  Mississippi  R,  water-worn,  rather  fine, 
99  to  110  Ibs/cu  ft;  voids  30  to  38  %.  Broken  limestone  from  near  St. 

*  Covered  with  thin  coat  of  rust,  but  without  scales.  The  others  fresh 
from  the  rolls  and  free  from  rust. 

fA.  L.  Johnson's  corrugated  bar,  Fig.  2d,  p  1130;  Expanded  Metal  and 
Corrugated  Bar  Co. 


EXPERIMENT   AND   PRACTICE. 


1169 


For  abbreviations,  symbols  and  references,  see  p  947 1. 

Louis,  80  to  95  Ibs/cu  ft,  passing  1%"  screen;  abt  half  the  stones  larger  than 
1",  about  one-tenth  of  the  stones  less  than^";  voids  42  to  48  %.  Voids, 
in  3  sand  +  5  agg,  16  to  19  %. 

Treatment.  Comp  specimens  left  in  molds  in  air  1  day,  beams  2  ds; 
then  all  in  water  2  wks;  then  in  air,  protected  from  drafts,  until  tested. 

Comp  specimens,  1  mo  and  1  yr  old,  loaded  4  to  8  times  per  min;  beams, 
1  mo,  6  mos  and  1  yr,  loaded  2  to  4  times  per  min. 

Results.  Effect  of  rate  of  repetition  insignificant;  but  be- 
lieved to  increase  rapidly  with  rates  above  10  per  min. 


oeated  load-i-max.  strength 

P  P  P  P  t- 

O  to  rf*.  OS  OO  c 

V 

^No.  of  Thousands  of  Repetitions  necessary  to  produce  failure. 
Fig  9.     Fatigue. 

Fatigue.  The  curve,  Fig  9,  fairly  represents  the  results  obtained  under 
these  varying  conditions. 

76  c.  Cone,  repeatedly  stressed,  below  the  fatigue  limit  (i.  e.,  below  about 
half  max  strgth,  see  Fig)  "has  imparted  to  it  a  definite  elastic  limit, 
within  which  stresses  are  proportional  to  strains"  (i.  e.,  within  which  the 
elastic  modulus,  E,  is  constant). 

76  d.  Fatigue  and  Adhesion. 

Specimens.  Plain  %"  square  steel  bars  imbedded  in  cone  as  above. 
Specimens  made  with  great  care  and  very  thoroly  tamped. 

Treatment.  In  molds  2  days,  in  water  7  ds,  in  air  3  wks.  30  fatigue 
specimens  subjected  to  "a  combined  blow,  pressure  and  the  accompanying 
vibration";  150  blows  per  min,  each  blow  =  740  inch-lbs.  Av,  50,000 
blows  to  each  specimen. 

Results.  Av  initial  adhesion,  125  Ibs/D"  of  imbedded  surf;  friction 
(after  slip)  90  Ibs/Q".  Uiifatigued  specimens,  150  and  100  Ibs/Q" 
respectively. 

76  e.  Fatigue  under  continued  load,  p  318.  2  cone  prisms 
remained  unaffected  for  a  month  under  90  %  of  their  crushing  strgth.  "A 
few  cone  blocks  failed  in  comp  in  a  few  hours  under  constant  pres  of  higher 


77.  Henry  S.  Spackmau. 

07,  Dec. 


Assn  Am  Port  Cem  Mfrs,   New  York, 


77  a.  Mortar  reground  after  hardening. 

Briquets   of   Port   cem,   broken    in   testing.     Reground   and   made  into 
new    briquets.     These   showed,    in   general,  about  half  the    tensile 

strengths  of  the  original  briquets.  Of  the  original  cem,  91.5  %  past  a 
No.  100  sieve,  76.2  %  past  No.  200.  The  reground  material  had  abt  the 
same  fineness. 

78.  R.  Feret,  A  S  C  E,  Trans,  '07,  Dec,  Vol  59,  p  152. 

78  a.  Permeability.     "  Experiments  give  in  general  uncer- 
tain results.     It  is  not  unusual  to  see  many  blocks  of  the  same  cone 

CIO 


1170 


CONCRETE. 


For  Directory  to  Experiments,  see  pp  1135-9. 

which,  altho  treated  in  an  identical  manner,  permit  very  diff  quantities  of 
water  to  filter  thru  them." 

78  b.  Age  of  block,  days  5  29  30  365 

Flow,  in  grams/min  per  Ib/Q* 

Presfrom71  to2841bs/D*;  Avge  0.554       0.044       0.159         0.294 

After  remaining  under  284  Ib/Q*  2  hrs     0.349       0.034       0.133         0.278 
78 c.  Percolation  "very  nearly  proportional  to  pressure." 

78  a.  3  blocks,  1  year  old.     Block  ABC 

Flow,  in  grams/min  per  lb/D" 

At2841b/sqm 0.067        0.111        0.108 

Raised  to 412  lb/D* 0.077        0.114        0.126 

Reduced  to  284  lb/D* 0.068        0.114        0.111 

"as  if  the  effect  of  the  momentary  increase  of  pres  had  been  to  open  new 
passages  for  the  water,  or  partly  to  clear  out  the  passages  already  existing." 

79     

79.  Wm.  B.  Fuller  and  S.  E.  Thompson.  A  S  C  E,  Trans,  '07, 
Dec,  Vol.  59,  p  67. 

Strength,  density  and  permeability,  as  affected  by  propor- 
tions and  character  of  sand  and  agg.  Expts  at  Jerome  Park 
Reservoir,  New  York. 

79  a.  Specimens.     Port  cem,  as  received  for  use  on  the  reservoir; 
agg  (1)  stone  and  screenings  from  crushers  at  reservoir,  mica  schist,  35  % 
mica,  which,  in  mortar  or  cone,  "does  not  form  planes  which  affect  the  strgth 
seriously."     (2)  Cowe  Bay  gravel  and  sand,  dredged  from  river  ("water- 
worn  rounded  bank  gravel  and  sand,  thoroly  clean,  and  consisting  almost 
entirely  of  quartz  particles."     Sp  gr  abt  2.65).     Max  size  of  stone,  2M", 
I",  yz". 


30 


10 


0  20  40  60  808.5       1010.6      12     13     Lt         15.9 

Pressure,  IBs.  iper  sq.  in.  Cement,  per  cent  of  total  dry  material. 

Fig-  1O.     Permeability. 

Tests  were  made  with  "  graded  mix  "  (proportions  giving  max  density 
of  agg)  and  "natural  mix"  (1  :  2.5  :  6.5,       1:3:6,       1  :  3.5  :  5.5). 
Results. 
79 b.  Size  of  aggregate;  strength  and  density. 

Max  stone  size,  inches 2H  1 

Relative  strength. 

Compression 1.00          0.83 

Transverse 1.00          0.91 

Cem  reqd  for  equal  strgth,  relative 1.00          1.17 

Relative  density 1.00         0.96 


1A 

0.72 
0.75 
1.33 
0.93 


EXPERIMENT   AND   PRACTICE.  1171 

For  abbreviations,  symbols  and  references,  see  p  947 1. 

79  c.  Kind    of   aggregate.     Sand  vs    screenings.     Relative 

strengths  and  densities. 

Comp  strgth  Transv  strgth       Density 

Sand  and  stone 100  100  100 

"        "    gravel 94  89  102 

Screenings  and  stone 67  85 

79  d.  Graded  mix  gave  density  =  1.14  X  density  with  natural  mix; 
for  equal  strgth,  graded  mix  reqd  0.88  X  the  cem  reqd  with  nat  mix. 

(This  means  an  av  saving  of  about  25  cts  per  cu  yd  of  cone.  Allen 
Hazen,  Trans,  A  S  C  E,  Vol  59,  p.  150,  Dec,  '07.) 

79  e.  An  excess  of  fine  or  of  medium  sand,  or  a  deficiency  of  fine  sand 
in  a  lean  cone,  diminishes  strgth  and  density. 

79  f.  Strength  and  density  max  when  mortar  just  fills  voids. 

79  g.  Permeability.  See  Fig  10.  "  Little  is  known  of  the  action  of 
cone  in  resisting  the  flow  of  water."  As  betwn  "diff  proportions  and  diff 
sizes  of  the  same  class  of  materials,  the  laws  of  watertightness  are  somewhat 
similar  to  those  of  strgth."  With  given  percentage  of  cem,  the  densest 
specimens  are  usually  most  watertight.  With  equal  densities,  the 
richest  specimens  are  most  watertight  (See  Fig).  The  ratios,  how- 
ever, are  very  diff  from  those  of  either  density  or  strgth,  a  slight  diff  in  the 
composition  producing  a  great  effect  upon  the  watertightness.  **  IMflr 
kinds  of  agg  produce  very  diff  results  in  watertightness."  Fig  shows 
effect  of  pressure  upon  permeability. 

79  h.  Cone  with  Jerome  Park  stone  and  screenings  gave  very  much 
higher  rates  of  percolation  thruout  (max,  369  grams  per  min)  than  that 
with  Cowe  Bay  sand  and  gravel.  Cone  with  stone  and  sand  gave  about 
half  the  rates  shown  in  Fig  10. 

79  i.  Permeability  is  sometimes  greater  with  large  and  sometimes 
with  small  stones.  Results  especially  erratic  with  the  Jerome  Park 
reservoir  broken  stone  and  screenings. 

79  j .  "  Permeability  decreases  materially  with  age ; "  increases  much 
more  rapidly  than  the  thickness  of  the  coiic  decreases; 

less  with  sand  and  gravel  than  with  stone  and  screenings; 

"    sand  ; 
"      "        "        "    stone        "  "    screenings ; 

80     

SO.  Richd  H.  Oaines,  New  York  Board  of  Water  Supply,  A  S  C  E, 
Trans,  Vol  59,  '07,  Dec,  p  159. 

8Oa.  Permeability  and  strength;  Clay  and  alum. 

Specimens.  Mortar,  1  :  3,  Portland,  Cowe  Bay  sand.  Tensile  testa 
on  standard  briquets;  comp  and  tensile  tests  on  2"  cubes.  Age  of  specimens, 
28  to  30  days.  Pressures,  40  and  80  Ibs/Q". 

Results.  (1)  Replacing  the  mixing  water  with  a  2.5  to  5  %  (1  to  2  % 
sufficient)  alum  solution  gave  nearly  complete  impermeability. 

(2)  Replacing  5  to  10  %  of  the  sand  with  dried  and  finely  ground  clay,  and 
(3)  combining  (1)  and  (2),  gave  still  better  results. 

The  clay  specimens  (with  and  without  alum)  showed  from  12  to  18  %  gain 
in  strength  over  those  without  clay. 

The  process  is  based  upon  a  theory  of  physico-chemical  action 
between  ions  of  the  electrolyte  (alum)  and  the  colloid  (glue-like)  molecules 
of  the  clay. 

None  of  the  processes  hitherto  in  use,  and  examined,  were  found 
suitable  for  extensive  use. 

Slaked  lime  slightly  decreases  permeability,  but  this  advantage 
is  more  than  offset  by  loss  of  strength.  There  is  no  chemical  reason  why 
this  should  be  otherwise. 


1172 


CONCRETE. 


For  Directory  to  Experiments,  see  pp  1135-9. 

81     

81.  Prof  E.  Morsch,  Zurich;  forWayss  and  Freytag  A.-G.,  Neustadt. 
"Der  Eisenbetonbau, "  Stuttgart,  Konrad  Wittwer,  '08,  to  which  the  pages 
given  refer. 

81  a.  Elastic  relations,  pp  27-32.  Specimens;  Square  prisms; 
measured  length,  35  cm  (13%").  1  part  Mannheim  Port  cem,  with  3  parta 
of  a  mixture  of  Rhine  sand  and  gravel  consisting  of  3  parts  sand,  0-5  mm; 
2  parts  gravel,  5-20  mm.  (0.197"-0.78").  Water,  14  %.  Each  stress  main- 
tained 3  mins.  Some  of  the  specimens  tested  in  tension;  the  others  in  comp. 

Compression)  in  millionfhs  of  original  length. 


( 

3           50          100         150         200         250         300         Zl 

0       S 
1400  g 

1200  | 
1900  | 
800  | 
600  § 
400  | 
200  | 

^ 

^ 

9oV*>^ 

_.. 

J)rij 

|S 

^'°T5 

^£- 

''  ^ 

x^ 

-60  0 

Elongation 


Fig  11.     Stress  and  Stretch. 


tf> 


Deformation,  in  millionfhs  of  original  length'. 
0  50          100         150         200         250         300 


2.5 

-50  0  50          100         150         200         250         300 

Deformation,  in  millionth*  of  original  length^ 

Fig:  12.     Elastic  Modulus. 

Results.     I'll  it  stresses  and  stretches  as  in  Fig   11.     Ult  ten- 
sions, Ibs/Q"  :  3  mos,  149;  2  yrs,  224. 
Elastic  Modulus,  E,  See  Fig  12. 
With  mix  1:4,  for  a  given  stress  in  comp,  E  was  in  general  from  15 


EXPERIMENT   AND   PRACTICE. 


1173 


For  abbreviations,  symbols  and  references,  see  p  947 1. 

to  20  %  less  than  with  1:3.     In  tension,  E  was  more  nearly  the  same  for 
both  mixes. 

With  water  8  %,  for  a  given  stress,  E  was  in  general  from  10  to  20  % 
higher  than  with  water  14  %. 

81  b.  Shear.  Fig  13.  Dimensions  in  centimeters.  Prisms,  18  cm 
square,  40  cm  long,  p  40.  Mixture  of  sand  and  gravel  as  in  Expt  81  a. 


Fig  13.     Shear. 

Plain.    Specimen  first  cracked,  as  beam,  at  a.    Pres  then  increased  until 
shearing  crack,  6,  appeared. 

Ult  av  shear,  Ibs/D"* 
No.  of 


Mix 
1  :3 
1  :4 


Water  % 
14 
14 


Age 
2     yr 
1.5  m 


Specimens 
3 
3 


Observed 
936 
530 


Calculatedf 
980 
550 


Reinforced.  The  bars  (1  cm  diam)  served  merely  to  hold  the  speci- 
mens together,  so  that  the  pres  could  be  increased  as  desired.  The  cone 
sheared  first. 

Ult  Av  shear,  Ibs/D" 


Mix 
1  :4 
1  :  4 


Age 
1.5  m 
1.5  m 


specimens 
2 
3 


Concrete 


522 

484 


Steel 
46400 
50800 


Water  % 
14 
14 

81  c.    B'orsioii.   p  45.     Mix,   1   :  4.     4  solid  cylinders,  79   to  98 

days  old;  26  cm  diam;  length  under  exp,  34  cm.  Hexagonal  heads.  M  = 
torsion al  moment;  R  =  radius  of  cyl; 

t  —  torsional  stress  in  extreme  fibers  (see  p  500,  this  book)  =  2  M/ir  R3 

t,  in  Ibs/D";  max,  275;  mean,  243;  min,  189. 

3  hollow  cyls,  as  above,  52  to  55  days  old;  inner  diam  abt  15  cm; 
r  =  inner  radius. 

t  =  2  M  R/it  (R*  —  r«), 

Z,.in  Ibs/D";  max,  134;  mean,  126;  min,  112. 

The  much  higher  unit  strength  of  the  solid  cylinders  as 
given  by  the  formulas,  is  attributed  partly  to  their  somewhat  greater  age, 
but  chiefly  to  the  increase  in  unit  stress  from  the  circumf  inward,  owing 
to  which  the  material  near  the  center  transmits  more  than  its  share  of  the 
torsional  stress,  and  thus  relieves  the  outer  portions. 

*  =  J/£  total  force  applied  -f-  area  of  one  shearing  surf, 
t  From  ult  tensile  strgth,  t,  and  ult  cornp  strgth,  c,  of  test  pieces  of  same 
mix  and  age,  and  formula,  shear  =  j/  t  c. 


1174  CONCRETE. 

For  Directory  to  Experiments,  see  pp  1135-9. 

81  d.  Adhesion,  p  49.     Figs  14  and  15. 

Specimens.     Cubes,  20  cm.     Mix,  1  :  4;    10  to  15  %  water;    age  4    wk& 
Round  bars  2  cm  diam,  Fig  15,  spiral  10  cm  diam  ;  wire  0.45  cm  diam. 


Fig  14. 

Adhesion. 


Fig  15. 

Treatment.     Bars  pushed  out.     Pres  rapidly  increased  to  max. 
Results.     Adhesion,  means  of  12  tests  each,  Ibs/D";   Fig  14,  adhe- 
sion =  518  ;  Fig  15,  adhesion  =  713. 

After  overcoming  the  adhesion,  considerable  frictional  resistance 

remained. 

81  e.  Ouctility  and  shear  in  reinforced  concrete,  p  00. 

Specimens.  4  reinforced  hollow  cylinders  in  torsion,  as  in 
Experiment  81  c,  reinforced  with  spirals  in  the  middle  of  their  wall  thick- 
ness. Spirals  at  45°,  so  placed  as  to  be  in  tension  under  the  twisting 
moment..  2  cyla  each  with  5  spirals  of  7  mm  round  iron,  two  cyls  each 
with  10  spirals  of  10  mm  round  iron.  Diam  of  spiral,  21  cm. 

Stresses  in  iron,  at  instant  of  first  cracking  in  cone,  Ibs/Q"; 
max,  8960  ;  mean,  8300  ;  min,  7700. 

Stretch  of  iron  and  of  cone  at  instant  of  first  cracking  in  cone,  av: 
0.00027  X  original  length. 

Foregoing  deduced  from  comparison  with  results  obtained  with  plain 
cyls  in  torsion,  Expt  81  c. 

Shear,   Ibs/D"  Max  Mean  Min 

At  first  cracking .  .  620  480  347 

At  rupture 767  624  430 

81  f.  Specimens.  6  reinforced  beams,  15  X  30  cm,  2  m  span, 
p  62.  Fig  16,  p  1175.  Dimensions  in  centimeters.  Thickness  of  reinfg 
bars  as  below.  2  concentd  loads,  P  P,  equidistant  from  cen  and  1  m  apart. 
Mix  1:4;  age  3  mos.  Measurements  on  central  length  of  80  cm.  Bendg 
mom  constant  thruout  this  length.  Stretch  of  steel  observed  by  means  of 
two  projecting  lugs,  at  A,  A,  screwed  into  the  bars.  Stirrups  provided  near 
ends  of  beams.  Beams  kept  wet,  but  tested  dry. 


EXPERIMENT   AND   PRACTICE. 


1175 


For  abbreviations,  symbols  and  references,  see  p  947 1. 


!<-15->i 


Fig  16.     Ductility. 

Results.    Stretch  per  unit  of  length  at  instant  of  first  cracking  of  cone: 

Cone,  under 


Bars  10  mm  (0.39")  diam  =  0.4  % 
"  16  "  (0.63")  "  =  1.0  % 
"  22  "  (0.86")  "  =  1.9  % 


Steel 
0.00042 
0.00033 
0.00030 


tension,  max 
0.00050 
0.00040 
0.00038 


81  g.  Steel  and  concrete  stresses,  p  97. 
Specimens.     Flat  reinforced  beams,  Fig  17. 


A,  3  beams  B,  S  beams 

Fig1 17.    Stresses.    Dimensions  in  centimeters. 

Bendg  mom  constant  betw  loads.    Mix  1  :  4.    Length,  2.2  m;  span  2  m. 
Results.     Failed  by  crushing  of  cone  near  and  betw  the  2  loads. 
Steel,  10  mm  diam. 

Unit  stresses,  s,  in  steel,  and  c,  in  cone,  in  Ibs/D",  deduced  under 
the  assumption  of  n  =  Eg/Ec  =  15. 

After  appearance 

of  first  cracks  At  rupture 


Age   Steel 

s 

C           8 

c 

3  beams  A  Fig 
3   "   B  " 

17  13  mo  1.4  % 
17  13  "  3.3  % 

22300 
20900 

1315      54000 
2250      39100 

3180 
4210 

3   "   A  " 
3   "   B  " 

17   2  "   1.4% 
17   2  "   3.3  % 

18600 
17000 

1095      44800 
1820      28000 

2630 
3000 

, 

'        CO 

i 

1.       «  = 

t-j  :  

1-  

i 

s 

! 

i 

25 

i 

u 

i 

U 

Fig  18.    Shear.     Dimensions  in  centimeters. 

81  h.  Shear  in  beams.  12  specimens,  each  consisting  of  a  flat 
plate  with  two  similarly  reinfd  ribs,  Fig  18.  Ribs  of  2.7  m  span  normal  t«? 
the  paper.  Der  Eisenbetonbau,  p  158. 


1176  CONCRETE. 

For  Directory  to  Experiments,  see  pp  1135-9. 

Types  of  web  reinforcement,  neglecting  slight  variations. 
Fig  19,  and  3d  col  of  table  below. 


c 

4,6,7,10,12 


Fig  19.     Shear. 

Stirrups:  4th  col,  table  below:  a,  thruout  span;  b,  in  one  half  of  span; 

c,  no  stirrups. 

Bars:  diam  in  mm:  a,  18;  b,  16;  c,  3  bars  15,  and  1  bar  18;  d,  2  bars 
15,  and  2  bars  16.     Beam  No.  3  had  3  straight  Thacher  bars,  18  mm  diam. 
Ends;  6th  col,  table  below:  a,  hook;  b,  plain;  c,  3  bars  45°,  1  hooked  ; 

d,  2  bars  bent,  2  hooked;  e,  3  bars  45°,  1  plain. 

In  No.  2  the  webs  were  0.28  m  wide;  in  No.  8,  0.10  m;  in  the  others, 
0.14m. 

Age,  about  3  mos.  Heidelberg  cem  1  :  4.5  (72  %  Rhine  sand  0-7  mm; 
28  %  gravel,  7-20  mm). 

Results. 


Stresses,  in,  Ibs 
s  =  tensile,  in 
at  support. 

1    §,! 

/D". 
steel  ;    c  =  comp,  in  cone  ;    a 

At  appearance  of 
diagonal  cracks 
which  lead  to 

=  adhesion; 

v  —  shearing, 

1  S 

w                  rupture 

"o 

At  rupture                       g 

| 

o   5  >»  :s  *  a        * 

»_3   PQ  H  w  W  W             » 

a 

V 

c 

s 

a 

V 

« 

.    1   a 

b   a 

a 

17900 

123 

149 

540 

29300 

198 

239 

1 

S    2   a 

b   a 

a 

34300 

234 

142 

824 

44800 

302 

183 

?, 

a 

b  .. 

b 

19500 

103 

132 

398 

27800 

146 

187 

3 

•"g     4   c 

c    c 

c 

36600 

382 

309 

881 

46300 

476 

384 

4 

^ 

p    5  d 

b  d 

d 

17900 

205 

146 

686 

37000 

418 

299 

5 

£ 

"6  c 

a   c 

e 

232 

186 

795 

42000 

432 

348 

6 

1 

a   b 

c 

924 

48600 

448 

318 

7 

*r> 

8    8d 

b  b 

d 

15800 

152 

152 

676 

34800 

324 

324 

8 

g    9d 

b  b 

d 

22500 

216 

141 

742 

38200 

352 

251 

9 

I 

<N 

<N 

S  10  c 

b   b 

c 

1100 

55000 

362 

257 

10 

S 

c  11  d 

o  b 

d 

1180 

54000 

357 

255 

11 

fl 

§  12  c 

c   b 

e 

1060 

53200 

348 

249 

12 

s 

*  The  positions  of  the  2  concentrated  loads  divided  span  into  3  equal  parts. 


EXPERIMENT   AND   PRACTICE.  1177 

For  abbreviations,  symbols  and  references,  see  p  947 1. 


Fig  20.     Diagonal  Stresses. 

82     

82.  Sanford  E.  Thompson.     A  S  T  M,  Procs,  '08,  Vol  8,  p  500. 
82  a.  Permeability.     Effect  of  admixture  of  slacked  lime. 

Specimens.  Cylindrical  blocks,  20"  diam,  16"  thick;  Lehigh  cem, 
good  av  bank  sand,  conglomerate  rock  resembling  trap  in  character;  "a 
soft,  mushy  mix,  such  as  would  be  adopted  in  construction."  Pine  Cone 
lime  from  Rockland,  Me.  Lime  stated  in  %  of  wt  of  dry  cem.  Mixtures 
as  follows: 

1:2:4      cone  with  0  %,  4  %,    7  %  and  10  %  lime;    8  %  preferred; 
1  :  2.5  :  4.5  "          '     0  %,  6  %,  10  %     "     14  %     "   ;  12  %  ; 

1:3:5        "        "     0  %,  8  %,  14  %     "    20  %     "   ;  16  %          "       . 
Treatment.     Water,  under  pres,  introduced  into  cen  of  block. 
Results,  1:2:4  and  1  :  3  :  5,  see  Fig  21.     1  :  2.5  :  4  gave  results  inter- 
mediate betw  the  other  two. 


Ing  per  hour. 

£  §  g  S  g 

\ 

\ 

\ 

\ 

X 

&— 

P 

\ 

s£ 

i 

I30 

|20 
810 

s 

^ 

\ 

^ 

^ 

> 

\ 

> 

^ 

\ 

'v^- 

^ 

"-  

0  5  10  15 

Percentage  of  hydrated  lime  to  weight  of  cement. 

Fig  21.     Permeability;  Lime. 

82  b.  Coarser  sand  requires  more  lime,  and  vice  versa. 

82  c.  If  pressure    is    to    be    applied    within    a   month,  it 

will  be  better  to  use  say  10  %,  15  %  and  20  %  respectively,  instead  of  8  %, 
12  %  and  16  %  as  recommended  under  Expt  82  a. 

82  d.  Lime  paste  occupies  about  2%  times  the  bulk  of  paste  made  with 
equal  wt  of  Port  cem,  "and  is  therefore  very  efficient  in  void  filling."     The 
cost  of  large    waterproof  work    may    be   reduced  by   using, 
with  lime,  a  leaner  cone  than  would  otherwise  be  suitable. 

83     

83.  Richard  1^.  Humphrey,  plain  cone  beams,  cubes  and  cylinders, 
comp  and  transv  strgths  and  the  elas  relations.  "The  Strgth  of  Cone 
Beams,"  U  S  G  S  Bull  No.  344, '08.  Tests  to  determine  the  effect,  upon 
transverse  and  compressive  strength,  of  (1)  age  of  specimen, 
(2)  consistency  of  mix,  (3)  character  of  aggregate. 

83  a.  Specimens.     Unreinfd  cone  beams,  cubes  and  cyls.     Cem,  a  mix 
of  9  Port  cems.     Meramec  R  sand,  "composed  of  flint  grains  having  com- 
paratively smooth  surfs."     "The  granulometric  analysis,  p  1178,  shows  the 
sand  to  be  rather  finer  than  desirable." 


1178 


CONCRETE. 


For  Directory  to  Experiments,  see  pp  1135-9. 

Properties  of  sand  and  aggregates  used. 

Meshes  per  inch  of  screen     Size  of  mesh,  ins 

200     100       50     30       10     '  H   %  "»£     1% 
Sp    Ibs/  voids  Percentage  passing  sieve  or  screen 

Kr     cuft    %      . , 

47  51  2.84  4.17  6.5  10.5  21.1  37  60  81  100 
41  1.59  2.29  3.2  4.4  8.5  20  58  99  100 
33  0  0  0  0  1.0  43  79  95  100 


Cinders 1.53 

Granite 2.59  95 

Gravel 2.45  102 

Limestone 2.49  98 

Sand 2.60  101 


37 
38 


2.96    3.48      4.2      5.2    10.7      29    61    96    100 
0.20    1.30    13.9    64.0   97.0    100    . 


Proportions,  1  :  2  :  4,  by  vol,  except  the  cinder  conc.which  was  nearer 
1:2:5.     All  cone  mixed  in  a  mortar-driven  cu-yd  mixer,  equipped   with 


charging  hopper.  Mixed  2  rains  dry,  3  mins  wet;  then  dumped  on  cem 
floor,  shoveled  into  barrows  and  wheeled  to  molding  floor.  Each  batch 
sufficient  for  2  beams,  8"  X  11",  12  ft  span,  two  6"  cubes  and  2  cyls,  8"  dia, 
16"  long. 

"Wet:"  smooth  and  somewhat  viscous  immedy  before  dumping. 
Flows  back  from  ascending  side  of  mixer  without  tendency  to  break  at  top. 
When  dumped,  shows  neither  voids  nor  individual  stones.  Splashes  when 
tamped.  When  finished,  water  stands  M"  to  yf  deep  over  surf  of  mold. 

**  Medium  "  :  smooth,  but  tending  to  lump.  Flows  less  smoothly  than 
"wet,"  part  flowing  back  smoothly  and  part  breaking  over  in  lumps.  When 
dumped,  looks  somewhat  lumpy,  showing  stones,  but  no  voids.  Stones 
evenly  coated  with  mortar.  No  water  collects  on  surf  in  mold.  Surf 
easily  finished  with  trowel. 

"  Damp " ;  granular.  But  little  tendency  to  lump.  Carried  to  top 
of  mixer  on  ascending  side;  falls  in  individual  stones  and  fragments  of  mor- 
tar. When  dumped,  shows  stones  and  voids.  Resists  tamping.  Compacts 
under  hand  tamping.  Cannot  be  finished  smooth  with  trowel. 

Cone  placed  in  oiled  steel  molds,  in  3  nearly  equal  layers,  and  hand- 
tamped.  "Great  care  was  taken  to  tamp  all  the  cones  in  the  same  manner. " 

Treatment.  All  molds  were  removed  at  end  of  24  hrs,  and  pieces  trans- 
ferred to  moist  room.  Sprinkled  3  times  daily. 

The  beams  were  so  supported,  just  prior  to  test,  that  the  sums  of  moments 
and  stressed,  then  existing  in  the  measd  length,  were  equalized,  so  that  all 
fibers,  in  that  length,  then  had  same  length  as  when  unstressed,  and  the 
deformations,  within  the  measd  length,  were  thus  measd  from  zero. 


"0  0.5  1.0  1.5  2.0  2.5 

G  1000  x  Deformation  per  unit  of  length. 

Fig  22.     Stress-stretch  curves  for  different  aggregates. 

Results. 

Stretches  and  comp  stresses  as  in  Fig.  22.     Medium  consistency.    Age,  26 
weeks. 


EXPERIMENT   AND   PRACTICE.  1179 

For  abbreviations,  symbols  and  references,  see  p  947  I. 

Strength  of  Concrete. 
Results,  in  general,  averages  of  3  specimens. 

Beams, 
8"  X  11",  12  ft  span         Max  comp  strgth,  Ibs/Q* 

Cylinders 
Neut     Rupt  modf         6  in  cubes       8"  dia,  16"  long 

Water    axis*    • • »  >•• " »     > " > 

%        100  m  4  wks  26  wks  4  wks    26  wks    4  wks    26  wks 
Cinder 

Wet 219       43.3       175       246  1,256     2,320     1,081     2,021 

Medm         ..20.6       39.9       198       277  1,191     2,765     1,201     2,203 


Damp  .  . 
Granite 

Wet 

Medm  .  . 
Damp 


18.9  38.2  198  250  1,378  2,488  1,118  1,945 

.   9.0  49.9  375  539  3,156  4,753  2,683  3,966* 

.   8.3  47.2  475  566  4,089  4,949  3,480  3.972J 

.    7.0  48.3  499  618  4,518  5,465  4,000  3,969t 


Gravel 

Wet  . .          .   9.7  49.9  391  435  2,299  3,814  2  060  3,486 

Medm 8.9  48.4  451  520  3,547  4,808  2,961  3,972* 

Damp 7.9  47.5  426  496  4,612  4,884  3,407  3,969i 

Limestone 

Wet..        ..10.9  48.8  422  507  5,141  3,460  3,072  3,216 

Medm 10.0  50.7  458  566  2,975  3,896  2,910  3,691 

Damp 8.5  48.1  537  589  4,367  5,025  2,894  3.942J 

84     - 

84.  R.  G.  Clark,  Inst  C  E,  Procs,  Vol  171,  '08,  p  115. 

84  a.  Time  of  setting-   increased  by  aeration  and  by  addition 

of  agg.     A  cem,  which,  neat,  sets  in  an  hr,  will  make  a  cone  requiring 
4  or  5  hrs  to  set. 

85     

85.  Hanisch  and  Spitzer,  Morsch,  Der    Eisenbetonbau,    '08,    pp 
32-33. 

85  a.  Rupture  modulus,  6  M  /b  d2,  and  direct  compressive 
and  tensile  strength. 

Specimens. 

Cone,  1  :  3.5.  Six  plates,  268  days  old,  60  cm  (24")  wide,  7.8  to  11  cm 
(3  to  4.5")  thick;  span,  150  cm  (60"). 

Treatment.  Plate  broken  transversely;  comp  and  tension  test  pieces 
made  from  the  fragments. 

Results.     Stresses  in  Ibs  /  D". 

Rupture  modulus       compression       tension 

max 775  5000  412 

mean  .  .  .  .  .682  4380  356 

min 614  3640  284 

Comparison  of  the  values  for  tension  with  the  rupture  modulus  shows  that 
the  formula,  rupture  mod  =  6  M  /  b  d 2,  is  not  applicable  to  materials  in 
which,  as  in  cone,  the  elas  mod  varies  widely,  and  that  the  rupture  moduli, 
obtained  by  means  of  the  formula,  are  to  be  used  only  as  a  means  of  compari- 
son. 

86     

86.  Richard  L.  Humphrey  and  Wm.  Jordan,  Jr.,  U  S  G  S, 

Bull  No.  331,  '08.     Results  of  Tests  made  at  the  Structural-Materials  Test- 
ing Laboratories,  St.  Louis,  '05-7. 

86  a.  Gravel  screenings.     In  general  the  tensile  and  comp  strgths 
of  mortars  seem  to  increase  with  density  of  screenings. 

*m  =  (depth  of  neut  ax  below  top  of  beam)  -=-  (total  depth  of  beam), 
t  "Rupture  modulus"   =  6  M  /bd2,  Ibs  /  D";  M  =  moment  under  max 
load. 

t  Cylinder  did  not  break, 

78 


1180 


CONCRETE. 


For  Directory  to  Experiments,  see  pp  1135-9. 


86  b.  Stone  screenings.  In  general,  strgth  of  mortar  was  greatest  with 
screenings  most  nearly  uniform  in  grading.  The  strength  of  the  stone 
itself,  from  which  the  screenings  are  derived,  has  an  important  bearing  on 
the  strgth  of  the  resulting  mortar. 

86  c.  Density  of  mortars  is  greatest  with  densest  sand. 

86  d.  Sand  mortars.  Tensile,  cpmpressive  and  transverse  strengths 
were  invariably  much  greater  with  dense  sands  than  with  those 
having  a  larger  percentage  of  voids. 

86  e.  Greatest  strgth  obtained  when  sand  is  uniformly  graded. 

86 f.  A  "typical  mix"  of  7  Port  cems,  like  the  separate  brands, 
reached  max  tensile  strength  in  90  days.  Like  the  best  of  these,  it 
maintained  this  max  to  180  els,  and  its  subsequent  loss,  at  one  yr  and  later, 
was  no  greater  than  for  the  best  of  the  separate  brands. 

86  g.  Age  of  briquet.  Tests  after  180  .days  showed  greater  uni- 
formity than  at  90  days  and  shorter  periods. 

86  h.  After  the  180  and  360  day  tests,  the  strgths  of  all  the  sand  mprtars 
were  reasonably  close  to  one  another,  showing  that  considerable  variation 
in  early  strength  does  not  seriously  affect  the  later  strength. 


1000 


180 

Age,  Days- 
Fig  24. 

86  i.  Tensile  and  Compressive  Strengths  of  Portland 
Cement  Mortars,  neat  and  1  :  3  standard  Ottawa  sand.  See  Figs  23  and 
24.  Each  curve  represents  an  av  of  10  tests. 


EXPERIMENT   AND   PRACTICE.  1181 

For  abbreviations,  symbols  and  references,  see  p  947 1. 

Specimens.  The  cem  was  a  mixture  of  equal  parts  of  7  diff  brands. 
See  Expts  86  f,  86  g  and  86  h. 

Test  pieces,  in  molds,  stored  in  moist  closet  24  hrs;  then  kept  in  running 
water,  abt  70°  F,  until  tested.  Tension  briquets  1  sq  inch  section.  Com- 
pression specimens,  2"  cubes. 

Results  as  in  Figs  23  and  24. 

87     

87.  W.    X.    Willis,  South  &   Western    R.    R.     E    R,  '08,    Jan    18; 
E  N,  '08,  Feb  6,  p  145. 

87 a.  Mica;  water  required;  strength. 
Specimens. 

Sieve  No 10  20  50  100 

%  of  mica  passing 100  29  10  4.5 

Sand,  Ottawa  standd.     Mortar  1  :  3  sand,  or  1  :  3  sand  and  mica  by  wt. 
Results. 

Mica ;  %  of  weight  of  sand 0          5          10         15          20 

Voids,  %  in  Ottawa  sand 37        67 

Relative  sp  gr  of  Ottawa  sand 100        ...        80 

Mixing  Water  required;  relative.  .      100        300 

Tensile  strength,  6  mos,  relative .      100        64         62         59          40 
The  smoothness  of  surf  of  the  mica  particles  renders  their  adhesion  low. 

88     

88.  Prof  J.  1^.  Van    Ornum,  Washington   Univ,    St.    Louis;    for 
Reinforced  Concrete  Constr  Co.,  St.  Louis.     E  N,  '08,  Feb  6,  p.  142. 

88  a.  Adhesion. 

Specimens.  Plain  round  steel  rods,  diams,  }/%  to  1  M",_  imbedded  in 
12"  X  12"  prismatic  blocks  of  1  :  2  :  4  cone,  90  days  old.  Medium  steel  rods 
imbedded  25  diams;  high  carbon  steel  rods,  40  diams. 

Results.     See  table  below,  in  which, 

for  Steel : 

s     =  Ult  strgth,  in  thousands  of  Ibs/D"; 

se    =  Elastic  limit,  in  thousands  of  Ibs/Q"; 

e     =  Elongation,  %; 

E    =  Elastic  mod,  in  millions  of  Ibs/Q". 

for  Steel  and  concrete: 

a     =  Area  of  imbedded  surf,  Q"; 

B    =  Adhesion,  Ibs/D"  of  a; 

F    =  Friction  after  flipping,  Ibs/D". 

Steel  Steel  and  Cone. 


Steel  s  ,          e          E  a  B      F      F/B 


Medium 
Max  

Av 

.     60.9 
.      58.6 

40.5 
39.1 

29.0 
26.1 

29.9 
29.5 

126.8 
62.1 

460 
408 

380 
342 

0.826 
0.838 

Min  
High  Carbon 
Max  
Av 

55.6 

.    109.6 
.     92.6 

38.4 

60.7 

56.1 

22.5 

20.7 
17.6 

28.6 

30.6 
29.8 

21.7 

198.3 
92.1 

370 

470 
392 

310 

280 
240 

0.838 

0.596 
0.613 

Min  

83.9 

53.1 

15.7 

28.9 

32.7 

330 

200 

0.606 

In  all  cases,  the  total  pull  which  overcame  the  adhesion  exceeded  that 
which  brought  the  steel  to  its  elas  lim. 

89     

89.  W.  S.  Reed.  Engrs'  Club  of  Phila.,  Procs,  Vol  25,  No  3,  p  290, 
'08,  Jul. 

89  a.  Friction  of  sand.  Exp  by  More  and  Harris  Tabor.  Top 
pres,  Ibs/Q",  reqd  to  give  10  Ibs/Q"  at  bottom  of  box. 


1182 


CONCRETE. 


For  Directory  to  Experiments,  see  pp  1135-9. 


Box 

4"  X  4" 
6"  X  6" 


Depth  of  sand,  ins 
2.5  5  7.5  10 

Top  pressure,  Ibs  /  D" 
12.5  17.5  34  42 

11-5  ....  26 


89  b.  Fusing  point  of  quartz  samls.  Exp  by  Prof  Heinrich 
Ries,  Cornell  Univ.  3254°  F. 

9O     

90.  Eng  News,  '08,  Aug  27,  p.  238. 

9Oa.  Sea  water.     Charlestown,  Mass,  Navy  Yard. 

Nonrein forced  arches,  built  '01,  by  Bureau  of  Yards  and  Docks 
Tidal  salt  water,  not  highly  polluted,  but  often  freezing;  range  of 
tide  10  ft.  Specification  called  for  "continuous  construction  from  pier  to 
pier  of  the  arch  rings. "  3"  mortar  face,  1:1.  Mass  cone  1  :  2  :  4  for  2  ft 
back  from  face,  1:3:6  interior;  "a  standd  cem  and  a  local  gravel." 
Probably  porous.  No  special  effort  toward  density  or  waterproofing.  Specfn 
provided:  "The  contractor  must  furnish  satisfactory  evidence  of  the  dura- 
bility in  sea  water  of  the  brand  of  cem  he  proposes  to  furnish."  The  show- 
ing spandrel  walls  weie  built  after  completion  of  arch  ring.  Dry,  well- 
tamped.  Serious  disintegration.  Damage  mainly  betw  H  W  and  L  W. 
Cone  backing  considerably  affected. 

91     

91.  U.  James    Nicholas,  Melbourne,  Victoria.     E  N,  '08,  Dec  24, 
P710. 

91  a.  Electrolysis  in  cement  mortars. 

Specimens.  16  cylinders,  8"  diam,  8"  high.  Standd  Port  cem  ;  coarse 
sand,  voids  51  %.  Mortar  tamped  in  1  Yi"  layers  until  a  little  water  flushed 
to  surf.  Positive  electrode,  normally  a  1"  steel  pipe,  12"  long,  lower  end 
corked,  immersed,  in  axis  of  cyl,  to  depth  of  5"  in  cone. 

Treatment.  Cyls  set  in  fresh  water  <  28  days.  8  cyls  tested  with 
constant  cnrrent  of  about  0.1  ampere;  5  with  constant  potential 
of  about  115  volts  (higher  currents,  one  with  reversed  current);  3  not  sub- 
jected to  current.  For  current,  cyls  placed  in  3  %  salt  solution  in  separate 
metal  pails  (which  normally  formed  the  negative  electrodes),  and  con- 
nected in  series.  Cyls  from  29  to  57  days  old  at  beginning  of  test. 

Results. 

All  cylinders,  under  current,  cracked.  Cracks  attributed  to  accumu- 
lation and  pres  of  liberated  gases.  Cracks  at  first  hair-like,  exuding  mois- 
ture, which  dampened  adjacent  surf.  Cracks  widened  under  continued 
current.  With  constant  current,  cracks  appeared  when  resistance  reached 
max.  Resistance  in  general  inversely  proportional  to  percentage  of 
sand.  Cyls  Nos  1  and  2  easily  pried  open.  In  Nos  2  and  9,  steel  pipe 
was  rusted  and  pitted  on  outside,  adjacent  to  crack.  With  (const 
potential)  reversed  current  (No  12),  no  rust  or  pitting. 

Cyls  not  subjected  to  current  were  not  cracked.  They  reqd 
about  20  blows,  with  heavy  hammer  and  cold  chisel,  to  break  them.  No 
rust. 


Constant  Current,  0.1  ampere 
No  of  Specimen. 

Constant  Potential, 
115  volts 
No  of  Specimen. 

1 

2 

9 

10 

13 

14 

5 

6 

3 

11 

12 

15 

7 

Mix  .. 

Sand,%.. 
Days*  .  .  . 

Mins*   .  .  . 
Ohmsf    .  . 

1  :3 

75 

7 

80 

1  :3 

75 

7 

90 

1  :1 
50 
10 

420 

1:1 
50 
16 

270 

15 
230 

15 
270 

1  :0 
0 

28 

2900 

1  :0 
0 
15 

1080 

1:3 
75 

'5' 
120 

1:1 
50 

19 
130 

1:1 
50 

20 

240 

258 

'9' 
163 

1:0 
0 

V 
190 

*  To  first  crack. 


t  Approximate  maximum  resistance. 


EXPERIMENT   AND   PRACTICE. 


1183 


For  abbreviations,  symbols  and  references,  see  p  947  I. 


92 


92.  «  H,"  of  Lafayette,  Ind. 

Clay.     In  cone  f 
to  top  in  churning,  and  left 


Letter  in  E  N,  '08,  Dec  31,  p.  751. 
gravel  contained  5  %  clay,  which 
worthless  material  near  top  of  col. 


92  a.   Clay.     In  cone  for  cols,  gravel  contained  5  %  clay,  which  floated 
of  w 


93 


93.  A.  Q.  Campbell,  Ogden,  Utah.     E  N,  '08,  Dec  31,  p  751. 

93  a.  Grading    and    impermeability.      Finish.      2     million 
gal  rectangular  reinfd  cone  water  tank,  20  ft  deep.     Floor,  6"  thick;  walls 
8  to  18".     1  cem,  2  ordinary  sand,  4  stone  (quartzite  boulders,  porphyry 
and  flinty  limestone)  crushed  to  1",  with  dust;  "a   heavy  percentage  of 
crushed  dust  and  sand"  ;  machine  mixt;   "consistency  that  would  almost 
pour."     Floor  laid  in  blocks  about  15  ft  sq,  "allowing  a  half-lap  of  2  ft;" 
walls   in   continuous  20*  layers.     Finish  of   1  :  1    cem  and  crusher   dust, 
applied  with  ordinary  broom  trimmed  short.     Clear  water.    No  perceptible 
checking  in  surf.     Apparently  no  seepage. 

-     94     - 

94.  John  C.  Trait  twine.  Jr.     '09. 

94  a.  I>ensity  of  sand;  shape  of  grain.    1  00  measures  of  rounded 
sand   grains,  or  of  angular  crushed  quartz  grains,  poured  very  slowly  into 
60  measures  of  water.     Exps  Nos  1  and  2  were  made  with  sand  grains;  Noa 
3  and  4  with  crushed  quartz  grains.     The  left  side  of  each  diagram,  Fig  25, 
represents  the  bottom  of  the  vessel;  and  the  numerals,  94,  121,  etc.,  show 
the  elevations  of  the  surfs  of  sand  and  of  water  respectively,  after  the  sand 
grains  had  been  poured  into  the  water. 


121 


Sand 


• 

•ii 

I 

98 

m 

1 

1 

106111 

H3 

1 

96 

Mi 

3 

20  40  60  80  100  120 

Elevation  of  sand  and  water  surf  aces  above  bottom  of  vessel. 
Fig  25. 

In  No  4,  the  crushed  quartz,  in  the  water,  was  stirred,  from  time  to  time, 
during  the  pouring,  in  order  to  liberate  any  air  which,  in  spite  of  the  slowness 
of  pouring,  might  have  been  carried  into  the  water  with  the  sand  grains. 
The  fact  that  the  water  stands  at  practically  the  same  ht  in  4  as  in  3,  indi- 
cates that  no  more  air  was  carried  down  in  3  than  in  4,  and  that  the  stirring 
merely  brought  the  grains  into  closer  contact  than  when  left  to  themselves. 


1184  CONCRETE. 

DIGEST    OF    SPECIFICATIONS,    ETC. 

FOR  GENERAL  CONCRETE  WORK, 

Pages  1186  to  1201. 
LISTS  OF  SPECIFICATIONS,  ETC,  USED. 

Alphabetical  List. 

See  Classified  List,  p  1185. 
(For  additional  abbreviations,  see  also  p  947  Z.) 

AH,  Algoma   Harbor,  Wis.,  Caisson   breakwater,  etc,  U.  S.  Engrs,  '08, 

Jan  24. 
BB,  Breakwater,  Buffalo,  N.  Y.,  Emile  Low,  U.  S.  Engrs  A  S  C  E,  Trans, 

'04,  Jun,  Vol  52,  p  73. 
BR,  Black  Rock  Harbor  and  Channel,  Buffalo,  N.  Y.     Ship  lock  walls. 

U.  S.  Engrs,  '07,  Dec  19. 

Bn,  Burlington,  Vt.,  Mechanical  filter  plant,  Hering  and  Fuller,  '07. 
Ch,  Chicago,  '08;  proposed  amendments  to  Building  Code  of  '05-6. 
Cl,  Cincinnati,  O,  Geo.  H.  Benzenberg; 

a,  Filters,  etc,  '05;  b,  Head-house,  etc,  '06. 
Co,  Columbus,  O,  John  H.  Gregory; 

a,  Filters,  etc,  '05;  b,  Pumping  station  and  intake,  '06. 
CR,  Columbia  River  impvmts,  Ore.  and  Wash.,  Canal.    U.  S.  Engrs,  '08, 

Aug  1. 
CS,  Concrete-Steel  Engineering  Co.,  Edwin  Thacher,  genl  specfns;  Melan, 

Thacher  and  yon  Emperger  patents,  '03. 
F,  Wm.  B.  Fuller,  Filters,  specification  received,  '08. 
FP,  Pensacola,  Fla.,  repair  and  protection  of  sea  walls.    U.  S.  Engrs,  08, 

Apr  18. 

FW,  Fort  Williams,  Me.,  Wharf,  Ship  Cove.     U.  S.  Engrs,  '08,  April  14. 
O,  General  practice. 

lib,  Harrisonburg,  La.,  Lock  and  dam  No.  2.     U.  S.  Engrs,  '08,  May  13. 
IM,  Illinois  &  Mississippi  Canal,  Locks,  Eastern  Section.    U.  S.  Engrs,  Jas. 

C.  Long,  Western  Soc  of  Engrs,  '01,  Apr,  Vol  6,  No.  2,  p  132. 
JC,  Recommendations  in  Report  of  Joint  Comm  of  A  S  C  E,  A  S  T  M,  Am  Ry 

Eng«&  M  W  Assn,  and  Assn  of  Am  Port  Gem  Mfrs,  '09,  Jan. 
L,  Louisville,  Ky.,  Building  Ordinance,  '07. 
JLp,  Liverpool  Harbor  Improvement,  Geo  Cecil  Kenyon,  A  S  C  E,  Trans,  '04, 

Jun,  Vol  52,  p  36. 

Lv,  Louisville,  Ky.,  Southern  Outfall  Sewer,  '07. 
Me,  McCall  Ferry  dam,  Susquehanna  River,  Pa.,  '08. 

Mh,  Manhattan,  Borough  of  — ,  Regulations  of  Bureau  of  Bldgs,  '03,  Sep. 
Ms,  Massachusetts  Legislature,  Acts  and  Resolves  of  the  — ,  '07. 
NO,  New  Orleans,  La.,  Water  Purification  Stations,  '06,  Sep  5. 
NY,  New  York.     Building  Code  approved  '99,  Oct  24,  with  amendments  to 

'06,  Apr  12. 
OD,  Ohio  R  below  Pittsburg,  Pa.,  Dam  No.  19,  Abutment.  U.  S.  Engrs, 

'08,  Jul  25. 
Ph,  Philadelphia.     Regulations  of  Bureau  of   Bldg  Inspection,  approved 

'07,  Oct  8.     Engrs'  Club  of  Phila.,  Oct  '07,  Vol  24,  No  4. 
SE,  Superior  Entry,  Wis.,  South  Pier,  Clarence  Coleman,  Asst  Engr.  Report. 

Chief  of  Engrs,  U.  S.  A.,  '04,  Part  4,  pp  3779,  etc. 
TR,  Tennessee  R,  below  Chattanooga,  Tenn.,  River  wall.  U.  S.  Engrs,  '08, 

May  27, 
TAT,  Taylor  and  Thompson,  "Concrete,  Plain  and  Reinforced,"  publisht 

by  John  Wiley  and  Sons,  New  York,  '05,  pp  33-37. 
Un,  Underwriters,  National  Board  of  Fire — ,  Building  Code  recommended, 

New  York,  '07. 

WII,  Waddell  and  Harrington,  general  specifications,  received  '07,  Dec. 
Wv.  Wellsville,  O.,  Navigation  pass,  Dam  No.  8,  near  — .   U.  S.  Engrs,  '08, 

To,  Yonkers,  N.  Y.,  covered  masonry  filters,  '07. 


CONCRETE   SPECIFICATIONS. 


1185 


Classified  List. 

See  Alphabetical  List,  p  1184. 

U.  S.  Govt  work,  AH,  BB,  BB,  CB,  FP,  FW,  Hb,  IM,  SE,  Wv. 

Breakwaters,  AH,  BB,  SE. 

Sea  walls,  FP,  SE,  TB. 

Locks  and  canals,  BB,  CB,  Hb,  IM. 

Harbor  improvement,  I«p,  SE. 

Wharves,  FW,  tp. 

Dams,  Hb,  MC,  O»,  Wv. 

Pumping  stations,  etc,  Ci  b,  Co  b. 

Filter  plants,  Bu,  Ci  a,  Co  a,  F,  NO,  Yo. 

Sewers,  I«v. 

Bridges,  CS. 

Building  codes,  Ch,  L,,  Mh,  Ms,  NY,  Ph,  Un. 

General,  CS,  JC,  T  «&  T,  WH. 


Outline  of  Contents. 


Subject 

Parag. 

Cement  

1 

Brand  

1 

Requirements  

2 

Shipment  

3 

Storage   

4 

Sand  

5 

Size  

.     6 

Screenings  

7 

Aggregate  
Kind  

8 
8 

Requirements  

9 

Sizes  

10 

Storage   

11 

Cinder  concrete   l: 

Large  stones 15 

Proportions,  see  p  1086. 
Measurement  of  ingredients  ....   21 

Consistency 22 

Mixing 28 

Hand  vs  machine 28 

Forms 34 

Lagging 34 

Tie  rods 36 

Placing,  churning  &  ramming  .  .   37 

Layers 40 

Joints 46 

Under  water 52 

During  rain 54 

During  freezing  weather 55 

Moistening 59 

Forms,  removal 61 

Freezing  weather 65 

Surface  finish,  etc   66 

Waterproofing    78 

Artificial  stone 80 

Strength,  etc  required 81 

Ultimate  compressive 81 

Ultimate  shearing 82 

Max  allowable  loads 83 

Compression 84 

Tension 91 

Shear 92 

Elastic  modulus 93 

Adhesion,    see    p    1111,    and    p 
1196,  H  113. 


Subject  Parag. 

Safety  factors 95 

Reinforcement 96 

Bars,  condition 96 

Shape 97 

Twisted 98 

Round,  corrugated,  etc 99 

Iron  and  steel,  requirements.  .  100 

Ult  tensile  strength 102 

Ult  compressive  strength  ....  103 

Fracture  104 

Elastic  limit 105 

Elastic  modulus 106 

Elongation  108 

Bending  test 109 

Max  allowable  stresses 110 

Adhesion 113 

Length  and  lapping 116 

Protection 117 

Permits 118 

Clearance 119 

Fireproof  bldgs 120 

Girders  and  columns  122 

Cinder  concrete 127 

Columns 129 

Rods  tied  together 133 

Requirements 136 

Cross-section  area 138 

Eccentric  loading 142 

Attachment  to  girders 143 

Hooped 144 

With  structural  steel 150 

Beams  and  floors .v 151 

Assumptions,  theory 151 

Stresses 155 

Adhesion 156 

Span.. 158 

Shrinkage,  etc 159 

Shear .  160 

Cement  finish 163 

Web  reinforcement 164 

Steel  in  comp  side 165 

Slabs  acting  as  flanges  167 

Moments 174 

Continuity 176 

Tests..,  ..183 


Cll 


1186  CONCRETE. 

For  lists  of  Specifications  for  Concrete,  see  pp  1184,  1185. 

In  order  to  compare  intelligently  the  requirements  of  diff  specfns,  the 
character  of  the  work  involved  must  of  course  be  taken  into  account. 

DIGEST. 
Cement. 

1.  Brand.     Portland  or  natural,  NY ;  Port  just  under  lower  miter  sill, 
nat  elsewhere  in  foundations,  Port  in  lock  walls  except  for  a  backing,  2  ft 
deep,  at  base,  Port  and  nat  bonded  together,  IM ;   for  reinforced  work, 
Portland,    G;    Am   Port,    CS,   BB,    Hb,    FW;     "Universal"    Portland 
cement,  SE ;  cem  made  by  mfr  of  established  reputation  (in  successful  opera- 
tion not  less  than  2  yrs,  F),  brand  in  continuous  successful  use  (in  America,  F) 
for  the  last  5  yrs  (3  yrs,  CS)  G ;  in  satisfactory  use  in  similar  quantities  by  U.S. 
Engr  Dept  at  Large,  TB;  of  tried  uniformity,  in  use  not  less  than  3  yrs  in 
similar  climate,  CB,  Hb;  only  one  brand  to  be  used,  G;  except  for  good 
reasons,  F ;  only  one  brand  in  any  monolith,  FP.    Portld  in  reinfd  work  and 
where  subject  to  shocks  or  vibrations  or  to  stresses  other  than  direct  comp; 
nat  in  massive  work  where  weight  is  more  important  than  strgth,  and  where 
economy  is  the  governing  factor;  puzzolan  only  for  foundations  underground, 
not  exposed  to  air  or  to  running  water,  JC. 

2.  Beqniremeuts.    For  Strengths,  etc.,  see  Digest  of  Specfn  for 
cem,  by  A  S  T  M,  p  940,  Report  of  Board  of  U.  S.  Engr  Officers,  Prof'l  Papers 
No  28,  Corps  of  Engrs,  U.S.A.,  '01,  p  937,  and  Digest  of  Specfn  by  Engng 
Standards  Comm  of    Great    Britain,  p  940.      For    tests,  see    Digest  of 
Specfn  of  A  SC  E,  p  942.  Slow  setting,  FP;  must  have  been  tested  <  6  mos, 
>  12  mos,  prior  to  issue  of  permit,  Ii;must  meet  requirements  of  Prof'l 
Paper  No.  28,  Corps  of  Engrs,  U.S.A.,  '01,  p  940,  BB,  AH,  TB,  CB, 
FW,  Wv,  FP,  HD. 

3.  Shipment.     Packages   to   "contain  either  380  Ibs  or   some   even 
division  of  380  Ibs, "  I^v ;  in  cooperage  or  in  cloth  bags,  NO ;  bag,  93  Ibs 
(94  Ibs,  Co)  net,  bbl  =  4  bags,  NO ;  in  bbls,  lined  with  paper,  CB,  WH ; 
in  cloth  bags,  Ci ;  may  be  delivered  in  paper  bags,  Wv. 

4.  Storage  at  site  of  work.     In  weather-tight  bldg,  with  floor  raised 
(<  6",  T  &  T)  above  ground,  G ;  and  holding  <  2  wks'  supply  under  ay  con- 
ditions of  work,  Ci ;  cem  in  bags  may  be  used  after  3  mos  storage,  rejected 
if  it  becomes  lumpy  or  otherwise  deteriorated  within  that  time,  BB ;  cem, 
kept  over  winter,  re-tested  before  using,  Wv. 

Sand. 

5.  General.     Silica,  hard,  clean,  sharp,  G.     Reasonably  clean,  coarse, 
F ;  water  worn,  voids  =  35  %,  SE.    "Sharpness'^purposely  omitted,  TAT. 
River  sand,  Ci,  a. 

6.  Size.     Well  graded,  with  fine,  medium  and  coarse  grains,  F,  l,v, 
NO,  Co.     Coarse,  or  coarse  and  fine,  mixed,  CS,  T  &  T.     Coarse  pre- 
dominating; coarse  preferred  at  double  or  treble  cost,  T  «fc  T.     Medium, 
Ci,  a.     Largest  to  pass  screen  of  %"  mesh,  G.      >  10  %  coarser  than  %", 
NO ;   <  50  %  retained  on  No.  30  sieve  (holes  0.022"  Q),WH.     >  40  %  to 
pass  No.  50  sieve  (2500  meshes  /  D"),  Hb.     >  3  %  very  fine,  NO,  Co, 
Ci,  a.      >  5  %  very  fine,  Bu. 

Foreign  matter  (clay,  loam,  sticks).  None,  CS,  T&T;  >  2% 
NO,  >  3  %,  Co,  I,v  ;  >  5  %,  Wv,  OI>,  TB,  CB,  Bu.  >  10  %  clayey, 
AH.  >  3  %  clay,  etc,  >  2  %  mica,  F W ;  >  4  %  free  loam,  Hb ;  sand  may 
be  moist,  not  wet,  TB ;  stored  on  a  board  platform,  CB ;  or  in  bins,  Wv. 

7.  Screenings.    Crusher  dust,  passing  Y\'  screen,  from  broken  stone, 
may  be  substituted  for  part  or  all  of  the  sand,  T  «fc  T ;  "screenings  &  crusht 
stone  may  be  substituted    for  sand  and  gravel  under  special  conditions," 
F;  screenings  permitted,  BB,  CB;  if  passing  M"  screen,  TB;  screenings 
preferred  to  sand,  AH. 

Aggregate  ("Ballast"). 

8.  Kind.   Sand  grit,  gravel  or  broken  stone,  BB ;  gravel  or  broken  stone, 
G;  or  both,  BB;  gravel,  I/v;  (see  Screenings);  sea-washed  gravel,  Lp; 
water-worn  pebbles  of  igneous  rock,  SE;  clean  stone,  gravel,  broken  hard 
bricks,  terra  cotta,  furnace  slag  or  hard  clean  cinders,  Un ;  broken  stone 

referred,  gravel  permitted  for  interior  of  piers,  pedestals  and  abuts,  WH ; 
in  stone,  AH. 


prefer] 
broker 


CONCRETE  SPECIFICATIONS.  1187 

For  abbreviations,  symbols  and  references,  see  p  947  I. 

9.  Requirements.     Clean,    hard,    durable;    free    from    dust,    loam, 
clay  and  perishable  matter;  washed  or  screened  if  reqd,  CJ;  approx  cubical, 
CS,  AH?  free  from  long  thin  pieces,  BR,  WO,  CS;  <  125  Ibs/cu  ft,  FP; 

<  130  Ibs/cu  ft,  Hb ;  voids  =  31  %,  SE ;  drenched  before  using,  « ;  but  not 
to  carry  water,  Wv;  kept  thoroly  sprinkled,  IM,  Hb. 

10.  Sizes,  inches:  min,  X,  G;  Ys,  FW,  Me;  max.  %,  Iln ;  1 J^,  Bii; 
2,  G;  21A,  Hb;  3,  XO,  Co,  Ci,  a,  FP,  SE;  gravel,  3,  F;  stone,  run  of 
crusher,  F,  Me,  AH;  1   to  2^,  according  to  grade  of    work,  AH;  for 
foundations,  2  ;  for  superstructure,  \%  ;  for  beams,  cols  and  girders,  1,  I«; 
gravel,  <  90  %  over  IK,  >  10  %  sand,  Hb. 

1  cubic  foot  of  stone,  gravel  or  sand  grit  contained 

Agg  cu  ft       Ibs  cu  ft      Ibs  cu  ft  Ibs 

Stone;.,    .coarse,  0.63     53.8;    fine,    0.33     30.4;    dust,  0.11     11 

Gravel;.  ..  pebbles,  %",  0.80     81.5;    sand,  0.29     29.2;  

Sand  grit;  gravel,  l/8"  to  %",  0.47     47.2;    sand,  0.59     59.3;  

BB. 

11.  Storage.     Stored  on  wooden  platforms,  CR,  Wv  ;  or  in  bins,  Wv. 

12.  Cinder  concrete.    Allowed  only  for  floors,  roofs  and  filling,  Ms. 
Reinfd    cinder  cone    to  be  used  only  upon  special  permit  of  Inspector  of 
Bldgs,  Lu 

13.  ' '  May  be  used  for  all  bldgs  in  which  fireproof  construction  is  mandatory 
by  this  Chapter,  or  where  ordinary  constr,  mill  constr  or  slow  burning  constr 
may  be  used,"  not  for  cols,  piers    or  walls.     Clean,  thoroly  burnt  steam- 
boiler  cinders;  mix,  Port  cem,  not  poorer  than  1  :  7.     Cinders  must  pass  1" 
sq  mesh,  Ch. 

14.  "All   other  special   requirements   and    methods    of  calculation   for 
reinfd  cone  as  reqd  in  this  Chapter  shall  modify  and  regulate  the  use  of 
cinder  cone  in  bldgs, "  Ch. 

15.  Large  Stones. 

Hard,  sound,  durable,  as  large  as  can  be  conveniently  handled;  washed 
clean;  placed  wet;  one  dimension  <  12";  no  dimension  less  than  4";  no 
stone  less  than  2"  from  faces  exposed  in  finished  work,  cone  joggled  into 
place  with  light  rammers,  Co. 

16.  >   100  Ibs,  <  3"  from   forms  or  from  other  large  stones.     (From 
Specfn  for  a  Soldiers'  Home.) 

17.  Permitted  in  walls  >  than   18"  thick,  diam  >  quarter  of  the  thick- 
ness of  wall,  vol  of  stone  >  one-fifth  vol  of  wall,  Yo. 

18.  One-man  stones  and  larger,  roughly  cubical;    long  flat  pieces  to  be 
broken  or  rejected;  stones  somewhat  uniformly  scattered  thruout  the  work; 

<  8"  apart,  <  2   ft  from  crest  or  down-stream  face;    dropped  separately 
into  bed  of  wet  cone,  pounded  down  if  necessary;   if  necessary,  cone  spaded 
under  and  around  the  stones;    each  stone  to  be  covered  with  cone  before 
other  stones  are  deposited.    Use  as  many  stones  as  possible  without  violating 
these  conditions,  Me. 

19.  "Plums."     Stones,  from  one-man  to  several  tons  (sometimes  from 
old  masonry),  aggregating  abt  30  %  of  the  finished  work    <  1  ft  from  wall 
surf.     Set  in  top  layer  of  cone  and  so  as  to  form  bond  with  next  layer  by 
projecting  upward  into  it,  L<p. 

20.  Proportions,  see  pp  1086  to  1090. 

Measurement  of  Ing-redients. 

21.  Cem  measd  "  as  if  compacted  so  that  380  Ibs  of  dry  Port  shall  have  a 
vol  of  3.8  cu  ft,"  L.V;  cem  measd  loose,  CS,  WH;  1  bag  cem  <  93  Ib  =  1 
cu  ft,  NO,  Ci.     Cem  measd  as  packt  by  mfr,  OD,  L,  T  «&  T.     Sand  and 
agg  measd  as  thrown  loosely  into  measuring  box,  €r.     All  measd  loose,  CS, 
WH;  100  Ibs  cem  considered  to  occupy  the  vol  of  1  cub  ft,  F. 

Consistency. 

22.  In  general,  "very  wet,"  5fO;  water  to  come  to  surf  with  moderate 
ramming,  CS;    without    serious    quaking,  OD,  TR;  sufficiently  fluid  to 
require  no  ramming,  Me;  little  or  no  tamping,  Hb. 


1188  CONCRETE. 

For  lists  of  Specifications  for  Concrete,  see  pp   1184,  1185. 

23.  (a)  For  ordinary  mass  cone,  such  as  foundations,  heavy  walls, 
large  arches,  piers  and  abuts;  medium  mixture,  of  a  tenacious  jelly-like 
consistency,  quaking  on  ramming.     T  <fc  T. 

(b)  For  rubble  cone  and  for  reinfd  cone,  such  as  thin  bldg 

walls,  cols,  doors,  conduits,  tanks;  very  wet    or  mushy,  so  soft  that 
it  must  be  handled  quickly  to  prevent  its  running  off  the  shovel.    T  «k  T. 

(c)  In  dry  locations  for  mass  foundations,  which  must  with- 
stand severe  comp  within  1  mo  after  placing,  "dry  "  cone,  consistency  of 
damp  earth,  provided  it  be  spread  in  6"  layers  and  rammed  until  water 
flushes  to  surf.     Not  permissible  in  reinfd  work,  TAT. 

24.  "  Sloppy."     Men,  spreading  cone  in  ultimate  position,  wear  water- 
tight leather  knee-boots,  and  are  ankle-deep  in  the  cone,  l<p. 

25.  In  foundations,  "sufficient  water  to  cohere  when  rammed    in 
place  by  30-lb  iron-shod  rammers;"  in  lock  walls,  enough  for  complete 
hydration  of  cem;  enough  for  coherence  after  thoro  mixing;  more  plastic 
than   damp   sand;    thoro    ramming   must    bring   water    to   surf;  incipient 
quaking  marks  the  limit;  any  excess  of  water  in  one  charge  may  be  corrected 
in  the  next;  consistency  varied,  from  time  to  time,  to  suit  conditions  of 
weather  and  constituents,  IM. 

26.  Cone  for  substructure  much  dryer  than  that  for  superstructure,  SE. 
Cone,  placed  under  water  to  be  semi-dry,  l»h. 

27.  Water  per  batch,  approx: 

3.5  cu  ft  per  batch  of  43.2  cu  ft,  making  28.5  cu  ft  rammed;  p  180; 

2.5  "    28.8      "  "         20.0     "  "       ;  p  179,  BB. 

Mixing. 

28.  Hand  vs  machine.    By  hand  for  foundations,  by  cubical  mixers 
for  lock  walls,  IM ;  by  cubical  mixer,  SE ;  by  machine,  F,  BR,  AH,  NO, 
Bu,  Co,  <'(,(>:  by  machine  when  amount  of  work  exceeds  1000  cu  yds, 
€S;  by  machine  in  general,  TR,  lib,  WH ;    "preferably  by  approved 
mixers  of  the  continuous  type  which  automatically  measure  and  feed  the 
correct  proportions  in  small  streams  into   the  mixing  chamber, "   F;  by 
batch  machine,  Bu,  Ci,  b ;  "  mechanical  batch  mixer .  .    ,  except  when  limit- 
ed quantities  are  reqd  or  when  the  condition  of  the  work  makes  hand  mixing 
preferable;  hand   mixing.  .  .only   when  approved  by  the   Bureau  of  Bldg 
Inspection,"  Ph;  batch  mixer,  Hb,  €R,  Wv,  FW;   <   100  cu  yds  per 
8  hour  day.'FW  ;  batch  mixers  preferred,  continuous  mixers  only  by  special 
written  permission  of  engineer,  WH. 

Method.  Materials  mixt  dry  before  adding  water,  C5S,  JfY;  turned 
_<  100  times,  Ci, b.  "In  all  mixing  the  material  shall  be  measd  for  each 
"batch;"  agg,  if  hot  and  dry,  to  be  wetted  before  going  to  mixer,  Ph.  One 
batch  completely  discharged  before  the  next  is  introduced.  Not  less  than  25 
revolutions  for  each  batch,  turning  cone  over  not  less  than  once  each  revo- 
lution, Un  ;  order  of  charging,  1st  gravel,  2d  cem,  3d  stone,  4th  water,  each 
batch  turned  <  2  mins,  >  9  revolutions  per  min,  extra  turns  to  be  given 
when  time  permits,  IM. 

29.  Batch  mixing.     Cem  (2  cub  ft  per  batch)  mixt  into  a  rough  paste 
on  platform.     First  pebbles,  then  sand  and  cem  paste,  then  broken  stone, 
dumped,  thru  hole  in  platform,  into  box  on  car  below.    Box  dumped  into 
mixer;  5  to  10  revolutions;  7  to  14  batches  per  hr.     With  14  batches,  12 
men  reqd  for  ramming,  BB;  first  sand,  then  cem,  then  agg,  then  water. 
TR,  Ol». 

30.  Hand  mixing.     Cem  and  sand  mixt  dry;  wet  stone  added;  water 
added,  €S.     Cem  and  sand  mixt  dry,  water  added,  agg  spread  not  more  than 
6"  thick,  sprinkled,  mortar  spread  over  agg  and  mixt,  Ph.     Cem  and  sand 
mixt  dry,  water  added,  mortar  mixt,  agg  (wetted)  added,  all  mixt,  Hb; 
mixture  of  sand  and  agg  first  spread  in  thin  layer  on  a  timber  platform, 
cem  spread  on  top,  mixt  dry,  turnd  over  as  water  is  gradually  added; 
broken  stone,  if  used  with  gravel,  is  added  wet  to  the  wet  mass,  WH. 

31.  On  tight  platform,  large  enough  for  2  batches  of  not  over  1  cu  yd 
each.     Cem  and  sand  spread  in  thin  layers  and  mixt  dry  until  of  uniform 
color. 

Then  use  either  one  of  3  optional  methods,  as  follows  : 
(1)  Mixture  of  cem  and  sand  spread  upon  layer  of  stone; 


CONCRETE  SPECIFICATIONS.  1189 

For  abbreviations,  symbols  and  references,  see  p  947  I. 

(2)  Stone  shoveled  upon  mixture  of  cem  and  sand.     In  (1)  or  (2),  turn 
3  times,  adding  water  in  first  turning. 

(3)  Mixture  of  cem  and  sand  made  into  mortar  and  spread  upon  stone. 
Mass  of  mortar  and  stone  turned  twice,  T  &  T. 

32.  In  any  case,  result  must  be  a  loose  cone  of  uniform  color  and  appear- 
ance, stones  thoroly  incorporated  into  mortar.     Consistency  uniform  thru- 
out,  T  «&  T. 

33.  "As  the  gravel  box  was  being  rilled,  the  cement  was  added  to  it 
gradually,   so   that,  when  the   gravel  box  was  full,  the  cement  box  was 
empty.     The  box  was  then  removed,  and  the  heap  leveled  off  to  a  uniform 
thickness  of  >  1  ft,  and  was  then  mixed  by  casting  backward  and  forward 
twice,"  water  added  at  time  of  second  casting,  Lp. 

Forms. 

34.  Lagging.    Of  well  seasoned  boards,  2"  thick,  drest  all  over,  tongued 
and  grooved,  Co,  b  ;  2"  X  6"  pine,  drest  on  all  sides,  Hb ;  boards  planed  on 
one  side  and  two  edges;  one  edge  slightly  beveled  and  placed  against  the 
square  edge  of  the  next  plank,  Yo ;  boards  preferably  2"  X  6",  dressed -and- 
matched  flooring,  WH ;  forms  for  exposed  faces,  of  planed  lumber,  tongued 
and  grooved  or  beveled;  wall  forms  to  be  braced,  and,  where  possible,  to 
have  their  sides  wired  together,  €i ;  butt  joints  square,  and  either  on  posts 
or  reinfd,  lib;  joints,  showing  spaces,  to  be  filled  with  stiff  clay  immedy 
before  placing  cone,  lib. 

Used  lagging,  if  not  scarred,  may  be  used  again;  but,  for  exposed  work, 
must  be  cleaned  and  oild,  Hb. 

Posts.  Generally  3"  X  8"  pine,  drest  on  both  edges,  of  full  height  of 
wall,  >  4  f t  apart,  Hb. 

Centers  and  forms  to  be  wet,  IM ;  if  reqd,  before  laying,  XO,  Ci,  b ; 
or  oiled,  XO.  According  to  circumstances,  forms  to  be  wetted  (except  in 
freezing  weather)  or  greased  with  crude  oil,  before  placing  cone,  T  &  T ; 
oild  just  before  use,  Hb;  painted  or  oild  before  re-using,  CB;  dampend 
just  before  placing  cone  and  kept  damp  until  work  has  hardened,  TK,  Wv. 

For  removal  of  forms,  see  p  1191. 

35.  On  up-stream  face  of  dam,  molds  need  be  only  smooth  enough  to 
give  good  substantial  work,  free  from  voids.     On  crest  and  down-stream 
face,  molds  must  have  planed  surfs,  so  as  to  leave  the  finished  work  smooth, 
Me. 

36.  Tie  rods,  left  in  cone,  must  not  come  nearer  to  cone  surf  than  2", 
CB;  projecting  ends  of  iron  bolts  and  rods  to  be  cut  off  smooth  and  flush 
with  cone  face,   I$K.  AH ;  not  chiseled,  but  sawn  or  otherwise  removed 
without  jarring  the  work,  AH;  aids  for  holding  molds  not  to  be  inserted 
within  4  ft  of  top  of  walls,  BB ;  no  bolts,  etc,  to  show  in  the  completed  work, 
OI>. 

Placing,  Churning  and  Bamming. 

37.  IXIght  work  prohibited  in  general,  TB.     Time  of  placing  ; 
cone  must   be  placed  within    30    mins    after    mixing,  AH,  XO,  Ci,  b ; 
>  30  mins  ' '  betw  wetting  the  cem  and  the  undisturbed  cone  in  final  place," 
F  ;  before  initial  set,  TB,  O»,  CB,  Wy,  FW,  Hb,  Bu ;  after  mixing, 
mass  kept  in  motion  until  placed  in  vehicle  for  transportation,  TB.     No 
s'etempering  or  rehandling  permitted,  TB,  CB,  WO,  Bn,  Co,  Ci,b, 
JC.     Cone,  in  which  the  materials    have  separated,  must  be  remixt  (by 
hand  mixing,   BB,  AH);  before  laying,  T  «fc  T. 

Manipulation.  In  very  wet  cone,  air  must  be  churned  out,  stones 
workt  back  from  face,  and  cone  workt  under  rods,  etc.,  CJ;  by  means  of 
thin  steel  or  iron  blades,  about  4"  X  6",  with  handles  of  adjustable  length, 
so  that  workmen  need  not  stand  in  cone,  5fO,  Ci,b.  Cone  to  be  joggled 
or  worked  into  place  by  light  ramming,  Bu,  Co  ;  ram  until  mortar  comes 
to  surface,  AH,  BB ;  until  all  voids  are  filled  and  water  flushes  to  the  surf, 
CS;  one  tamper  to  not  more  than  2  cu  yds  per  hr,  BB;  rammers  with 
striking  area  not  less  than  36Q",  weighing  not  more  than  10  Ibs,  Co; 
face  6"  sq,  weight,  with  handle,  about  20  Ibs,  CB ;  30-lb  iron-shod  rammers, 
face  area  not  more  than  30Q",  IM ;  40-lb  rammers,  SE ;  cone  placed 
without  ramming,  FP. 


1190  CONCRETE. 

For  lists  of  Specifications  for  Concrete,  see  pp  1184,  1185. 

38.  Dry  cone  moistend  by  sprinkling,  not  pouring,  €R. 

39.  Cone  must  be  continuously   worked  around  reiiifmt,  with 
suitable  tools,  as  put  in  place.     Complete  filling  of  forms,  and  subsequent 
puddling,  prohibited.     Partly  set  cone  must  not  be  subjected  to  shocks,  Ch. 

40.  Placing-,  in  layers.     Care  taken  to  remove  all   scum,  arising 
from  the  cem,  before  laying  the  next  layer,  l«p,  JC. 

41.  Cone  dumped  from   receiving  box  or  car,  or  shoveled  directly  into 
place,  use  of  slides  and  shutes  forbidden,  OD,  Wv,  FP,  TB,  CB :  not 
dropt  further  than  6  ft,  FP ;  3  ft,  Wv. 

42.  No  walking  on  finished  wall  until  set,  OD,  Co. 

43.  Thickness  of  layers.     Not  over    6",    Wv,  BB,  OD ;  about 
6",  CB;  about  6"  after  ramming,  TB:  6  to  8",  CS;   >  6",  F;  >  4",  SK: 
with  dry  mix,  on  slopes,  >  4",  F ;   >  4"  in  foundations,  about  6"  in  back 
walls,  IM;   >  9",  Hb;   >   12",  WH;  such  that  each  layer  can  be  incor- 
porated with  the  preceding  one,  T  «fc  T. 

44.  No  layers  permitted,  Bu,  Co  ;  layers  not  run  out  to  thin  edge,  FP ; 
each  layer  completed  (rammed,  CB)  before  the  next  is  laid,  FP,  CB; 
each  layer  of  a  day's  work  laid  before  the  layer  next  below  has  set,  TB. 

45.  On  rock  foundation.     Rock    cleaned    and    washed  with    wire 
brooms,  roughened   if  reqd,  covered  with  thick  neat  cem  grout,  CB :  bed 
of  wet  mortar,  FW;  }/<£  thick,  TB;  cone  anchored  to  rock  with  steel  rods, 
if  reqd,  CB. 

Joints. 

46.  Avoidance  of  horizontal  joints.     Walls,  etc,  built  in  alter- 
nate sections,  so  short  that  they  can  be  constructed  as  monoliths;  these 
sections  keyed  together  by  vertical  tongue-and-groove  joints,  O  for  gov't 
specfns;  joints  continuous  from  foundation  to  coping,  CB  ;   "  joints  shall  be 
formed  betw  adjoining  sections  of  cone  for  4  ft  down  from  the  deck,  by  a 
layer  of  tarred  paper,"  BB ;  dovetailing  to  have  a  thin  coat  of  mortar,  1  :  5 
or  weaker,  to  set  before  new  cone  is  placed  against  it,  Hb. 

47.  Joints  between  old  and  new  work.     Exposed  surfs  shaded 
and  kept  moist  until  work  is  resumed,  CB ;  chipped  or  broken  edges  cut 
away,  CB ;  old  surf  to  be  left  stepped,  to  form  bond,  and  to  be  cleaned  and 
wet  before  adding  new  work,   FW,  O ;  cleaned  with  stiff  wire  brush  and 
stream  of  water,  FP,  BB,  Hb ;  if  reqd,  F,L<v ;  roughed  up  with  a  pick, 
if  reqd,  BB  ;  wooden  strips,  4  to  6"  wide,  with  beveled  sides,  to  be  embedded 
<  3",  and  removed  before  cone  has  thoroly  hardened,  NO  ;  between  old  and 
new  work,  bed  of  1  :  3  cem  mortar  1"  thick,  NO,  Co ;    y<j'  layer  of  mortar, 
FP;  old  surf  covered  with  neat  cem  grout  of  molasses  consistency,  BB;  or 
dry  cem,  OD ;   dry  cem,  brushed   in,  Hb ;    with  layer  of  mortar,  TB, 
F W ;  old  surf  mopped  with  1  :  2  mortar,  CS ;  with  heavy  neat  cem  grout 
worked  into  surf  with  brooms,  CB;  keyed  as  directed,  FW. 

48.  In  hqr  joints  in  thin  walls,  or  in   walls  to  sustain  water  pres, 
or  in  other  important  locations,  mortar  joint  may  be  reqd.     Tanks,   etc, 
with  thin  walls  to  hold  water,  should  be  built  as  monoliths,  without  inter- 
ruption, the  work  proceeding,  if  necessary,  night  and  day,  T  «fe  T. 

49.  When  work  is  suspended   for  more  than  an  hour,  the  outer 
edges  of  the  last  layer  are  to  be  leveled,  and  the  center  portion  of  the  surf 
is  to  be  left  about  6"  lower  than  the  edges,  CB. 

50.  Bond  betw  new  cone  and  old  wall.     Dovetailed  pockets,  24"  wide  at 
face,  33"  at  back,  15"  deep,  cut  vert  in  old  masonry,  4  ft  apart,  I^p. 

51.  Last  layer  deposited  to  be  left  as  rough  as  possible,  imbedded  bould- 
ers projecting.     Surf  to  be  cleaned,  washed,  and  sprinkled  with  neat  cem, 
JMLc» 

Placing-  under  Water. 

52.  IJnder  water.     No  cone  to  be  laid  under  water  (without  explicit 
permission,  F;  except  to  stop  leaks  and  springs,  TB;)  water  not  allowed 
to  rise  on  new  work  until  thoroly  set,  IM,  Wv,  TB,  OD;  not  less  than 
24  hrs  after  set,  tv,  NO,  Co,  Ci,b;  if  placed  under  water  before  set- 
ting, mixture  to  be  1  :  2  :  3,WH;  80  %  of  work  built  in  place  below  (fresh) 
water  level,  SE ;  cone,  placed  in  water,  must  be  semi-dry,  Ph  ;  bags  to  be 
lowered  to  within  a  few  ins  of  surf  on  which  cone  is  to  be  deposited,  FW, 


CONCRETE   SPECIFICATIONS.  1191 

For  abbreviations,  symbols  and  references,  see  p  947  1. 

53.  When  forms  extend  down  to  below  high  water,  leaks  under  forma 
to  be  stopped,  in  order  to  prevent  undermining  before  set;  bags,  filled  with 
sand,  placed  outside;  or  jute  canvas,  underlying  the  cone  12",  nailed  along 
bottom  of  form  on  the  inside,  FW. 


54.  Rain.     During  rain  storms,  no  new  work   to  be  laid,  IM,    Bn, 
,  FP;  freshly  laid  work  to  be  protected  by  canvas, 


Frost. 

55.  Freezing.     No  concrete  or  mortar  to  be  made  when  temp  is  below 
35°  F.  in  shade;  cone  work  stopped  from  Nov  20  until  April  1  ;  during  freez- 
ing weather,  no  cone  to  be  mixed  or  deposited  without  engineer's  consent, 
IM,  Bu;  ice  and  frost  to  be  removed,   water  and  sand  heated,  gravel 
steamed,  work  covered  and  kept  warm  by  steam  pipes,  JLv  ;  cone  not  to  be 
placed  when  frozen;  if  reinfd,  must  be  kept  above  32°  F  for  <  48  hours 
after  placing,  use  of  frozen  sand  and  agg  prohibited,  Ch.     No  laying  per- 
mitted when  temp    >  32°  F.,    IJii,  AH,  BR,   <  32°  F,  O»;   <  30°  F, 
CR,  <  34°  F.,  TR,  FP  ;  when  likely  to  freeze  before  set,  Wv  ;  before 
final  set,  OI>  ;  before  set  sufficiently  to  prevent  injury,  BR,  CR.     Cone, 
frozen  in  place,  to   be  removed,  Uii.     No  cone   to  be  laid  when   temp  is 
below  20°  F;  water  to  be  heated  when  temp  is  below  35°  F,  Me.     Use  of  icy 
materials  prohibited;  placed  cone  must  be  protected  against  freezing,  Ph. 

56.  Natural  cement  concrete  must  never  be  exposed  to  frost  until 
thoroly  hard  and  dry,  T  «&  T. 

57.  "No  cone,  except  that  laid  in  large  masses,  or  heavy  walls  having 
faces  whose  appearance  is  of  no  consequence,  shall  be  exposed  to  frost  until 
hard  and  dry.     Materials  employed  in  mass  cone  in  freezing  weather  shall 
contain  no  frost.     Surfs  shall  be  protected  from  frost.     Portions  of  surf 
cone,  which  have  frozen,  shall  be  removed  before  laying  fresh  cone  upon 
them."  T  &  T. 

58.  Forms,  under  cone  placed  in  freezing  weather,  "  to  remain  until 
all  evidences  of  frost  are  absent  from  the  cone,  and  the  natural  hardening 
of  the  cone  has  proceeded  to  the  point  of  safety  ."     Cli,  Ph. 

Moistening. 

59.  Moistening1.     Freshly  laid  cone  to  be  protected  from  the  sun  (by 
boards  or  tarpaulins,  FP,  Hb,  IM;)    and  kept  wet,  Me,  IM  ;   <  two 
weeks,  or  until    covered  with    earth,    F  ;    <   10   days,    SE,  AH  ;    6  ds, 
CR  ;  3  ds,  FW  ;  48  hrs,  BR  ;  until  set,  Wv  ;  until  hard  set,  Hb  ;  unfinished 
surfs  until  work  can  be  resumed,  CR;  with  wet  tarpaulins  <  3  days,  CR. 
When  a  section  of  wall  is  completed,  coping  to  be  covered  with  a  thick  layer 
of  wet  sand,  mass'of  wall  kept  sprinkled  until  cone  is  thoroly  set,  IM  ;  cone 
to  be  drenched  twice  daily,  Sundays  included,  for  a  week  after  placing,  in 
hot  weather,  Ch,  Ph. 

60.  Moisten  by  sprinkling  with  fine  spray  at  short  intervals  or  by  covering 
with  moistened  burlap,  or  etc,  O. 

Removal  of  forms. 

61.  Forms  must  be  left  in  place  <  4  days,  IM  ;   <  7  ds;  longer  if  reqd 
by  engineer,  I,v  ;  72  hrs,  OI>  ;  48  hrs,  AH,  BR  ;  until  cone  has  stood  at 
least  36  hrs,  WH  ;  until  renwval  is  authorized  by  engineer,  or  until  cone 
has  become  hard,  Ci,b  ;  until  cone  can  carry  its  load  safely,  Ms;  forms 
removed  after  48  hrs,  SE. 

62.  Props,  under  floors  and  roofs,  to  remain  in  place  <  2  weeks.     Forms, 
for  cols,  <  4  days;  for  slabs,  beams  and  girders,  <  1  wk  and  at  least  until 
the  floor  can  sustain  its  own  weight.     "No  load  or  wt  shall  be  placed  on 
any  portion  of  the  constr  where  the    said  centers  have    been    removed." 
Ch,  Ph. 

63.  Time  for  removal  of  forms  and  centering,  24  hrs  to  60  days,  depending 
upon  temp  and  other  atmospheric  conditions  and  upon  the  commissioner 
of  bldgs,  Un. 


1192  CONCRETE. 

For  lists  of  Specifications  for  Concrete,  see  pp  1184,  118d. 

64.  Not  until  cone  is  hard.  Min  time,  days: 

Apr  1  to  Dec  1     Dec  1  to  Apr  1 

Slabs  and  lintels,  cols  and  monolithic  walls  10  15 

Posts  and  bottom  supports  for  joists,  beams 

and  girders 14  21       Li. 

65.  Forms,  under  cone  placed    in  freezing  weather,   "to   remain 
until  all  evidences  of  frost  are  absent  from  the  cone  and  the  natural  harden- 
ing of  the  cone  has  proceeded  to  the  point  of  safety."     Ch,  Ph. 

Surface  finish,  waterproofing-,  etc. 

66.  Finish  kept  smooth  by  manipulation  during  placing,  not  by  subse- 
quent plastering,  etc.    Cone,  free  from  large  agg,  to  be  placed  next  the  mold, 
and  prest  back  from  mold  by  means  of  a  flat  shovel,  inserted  betw  cone  and 
mold  (mold  sprinkled  with  water,  II 11),  cone  rammed  with  an  iron  rammer, 
lower  face  2"  X  6*,  AH,  BR ;  finish  by  working  gravel  back  from  face  by 
means  of  forks,   lib:  or  shovels,  FP;  faces  rubbed  smooth,  Tit.    lib: 
with  a  piece  of  wood  or  soft  stone,  TR ;  voids  filled  up  with  mortar,  lib. 
TR,  CR;    plastering    permitted    only  for    an    occasional  and    accidental 
cavity  where  the  plastering  is  not  apt  to  be  disturbed  by  frost,  CR.     See 
p  1193,  If  79.     1  :  3  Port  cem  mortar,  placed  simultaneously  with  backing, 
€R.     For  wall,  1  :  2  Port  cem  mortar,  very  dry,  1  >#"  thick,  TR. 

67.  For  exposed  faces,  forms  to  be  removed  before  cone  has  hardened; 
surf  (1)  rubbed  with  mortar  of  1  vol  Port  cem,  2  vols  sand,  applied  with  a 
burlap  swab  and  brushed  down  with  a  plasterer's  brush,  or  (2)  rubbed  with 
stiff  wire  brush  and  a  thin  coat  of  neat  Port  cem  grout,  brushed  down  with 
plasterer's  brush,  NO,  Co ;    smooth  finish    of  sides  produced  by   thoro 
ramming  against  inside  surfs  of  molds,  &E. 

68.  Surfs,  not  built  against  forms,  screeded  and  troweled  to  smoothness, 
NO. 

69.  Voids  or  other  imperfections,  appearing  upon  removal  of  forms,  to 
be  corrected  at  expense  of  contractor,  who  shall  remove  and  replace  unsatis- 
factory work  if  reqd,  F. 

70.  For  floors  and  roof  of  mixing  tank.     Stiff  mortar,  of  1  vol 
Port,  1  vol  sharp  stone  screenings  to  pass  %"  ring,  free  from  dust,  loam,  etc,  1" 
deep,  laid  before  cone  has  initial  set.     Screeded,  floated  and  troweled  to 
smooth  surf.     Covered  and  sprinkled  3  days,  Co. 

71.  Pronienades  and  tops  of  parapets  finished  with  a  layer  of 
mortar  ~>   %"  thick,  consolidated  with  the  cone  "by  superimposing  heavy 
planks  4"  thick  and  ramming  them  with  40-lb  cast  iron  rammers  until  their 
ends  are  in  contact  with  the  ends  of  the  molds,"  SE. 

72.  For  piers,  pedestals,  abutments.     Surfs  exposed  to  air  or 
water,  1  J^"  Port  cement  mortar,  1   cement,  2  sand,  carried  up  simultane- 
ously with  the  cone,  10  or  11"  in  depth  at  a  time,  by  means  of  W  steel 
plate  forms,  12"  wide,  4  to  5  ft  long,  placed  around  the  work,  1  ]/y  from  the 
forms,  and  blocked  out  every  12"  by  wooden  blocks,  the  ends  of  the  plates 
lapping  slightly,  WH. 

73.  For  inverts,  1  cem,  2  sand,  not  more  than  }/(?  thick,  laid  at  same 
time  as  cone,  I.V. 

74.  Moldings,  cornices,  etc.     Plastic  mortar  placed  against  finely 
constructed  molds,  as  cone  is  being  laid;  no  exterior  plastering  permitted, 
SE,  T  &  T;  no  plastering  to  be  done  unless  expressly  permitted,  F. 

75.  Top  finish.     Cone  brought  up  to  3  J^"  from  reqd  elevation;  while 
this  is  still  unset  and  plastic,  3"  of  finer  cone  added,  tamped  and  kneaded 
to  form  a  monolith  with  the  underlying  cone;  then  Y<j'  of  1  :  3  (1:2,  AH) 
cem  mortar  added  and  worked  down  to  reqd  grade  by  rubbing  with  a  long 
wooden  straight-edge,  AH,  BR. 

76.  Coping.     While  cone  base  is  still  soft,  unset  and  adhesive,  mortar 
(to  be  1"  thick  when  finished)  spread,  leveled  off  and  beaten  with  wooden 
battens  or  mauls;  floated  with  wooden  float  and  smoothed  with  plasterer's 
trowel;  covered  with  boards  or  tarpaulins  until  hard  set;  then  covered  with 
sand;  to  be  kept  damp  several  days,  FP ;  mort.ar,  <  1"  thick,  of  375  Ibs 
Port  cem  to  10.5  cu  ft  sand;  tamped  in  place  on  top  of  rammed  cone  before 
the  latter  has  begun  to  set;  raked  with  straight-edge,  rubbed  with  wooden 


CONCRETE   SPECIFICATIONS.  1193 

For  abbreviations,  symbols  and  references,  see  p  947  I. 

floats  and  finished  with  plasterer's  trowel,  CR;  1  :  2  Port  cem  mortar,  1" 
thick,  TR;  surf  formed  by  working  the  stones  back  from  face,  Hb. 

77.  Granitoid  surface  finish  for  tops  of  piers,  pedestals  and  abuts; 
1  part  Port,  2  parts  clean  coarse  granite  sand  or  fine  granite  screenings,  3 
parts  granite  chips,  passing  y?  iron  ring.    Finished  with  a  floated  surf.  WH. 

78.  Water-proofing-.     Heavy  coat  of  semi -liquid  mortar  1  part  cem, 
H  part  slaked  hme,  3  parts  sand.     This  coat  to  be  given  a  smooth  finish. 
When  this  has  set  hard,  add  a  heavy  coat  of  pure  cem  grout,  CS. 

79.  Plastering-  with  cement.     None  permitted  on  exposed  faces, 
AH,  €S.     Inside    faces    of   spandrel    walls,  covered    by    fill,  to    be    well 
dampened  and    plastered  with  mortar    of    1  cem  :  2.5  sand,  CS.     See  p 
1192,  U  66. 

Artificial  stone. 

80.  (a)  For  fine  moldiiig-s,  etc.     M9lds  plastered  with  semi-liquid 
mortar,  1  cem,  2  fine  sharp  sand,  backed  with  earth-damp  cone  1  :  2  :  4, 
or  1  cem  to  6    gravel    passing  ?£"  ring.     Cone    backing    rammed    in   thin 
layers,     (b)  For  plain  flat  surfaces.     Cone  rammed  in  mold.     Mold 
removed.     Exposed  surfs  floated  to  smooth  finish  with  mortar  as  in  (a). 
No  body  of  mortar  to  be  left  on  face.     Use  only  enough  to  fill  pores  and  give 
smooth  finish,  CS. 

Streng-th,  etc,  required. 

(Strengths,  etc,  in  Ibs  /  D",  unless  otherwise  stated.) 

81.  Ultimate  comp,  after  hardening  for  28  days,  <  2000,  Un,  Mh. 

82.  Ult  shear  corresponding  to  2000  comp,  200,  Un. 

Maximum  allowable  loads. 

83.  For  static  loads  upon  a  1  :  6  Port  cem  cone. 

Max  allowable  load 

Ibs  /  Q"t 

Compressn,  cone  surface  >  loaded  area 0.325. s*=  650 

in  columns,  length  >  12  diams 0.225 .      =  450 

with  longitudinal  reinfmt  only 0.225.      =450 

hooped 0.270.      =  540 

,  with  1  to  4  %  long'l  bars  .  .  .0.325.      =  650 
with  structural  steel  col  units  thoro- 

ly  encasing  cone  core 0.325.      =  650 

Rupture  modulus  (elas  mod,  E,  constant) 0.325.      =  650 

adjacent  to  supports,  (E  constant) 0.375.      =  750 

Pure  shear  (no  comp  normal  to  shearing  surf;  reinfmt  tak- 
ing the  normal  tension) 0.060.      =   120 

Shear,  combined  with  equal  comp 0.162.      =  325 

Adhesion,  plain  bars 0.040 .      =     80 

drawn  wire    .  ...0.020.      =     40 

JC. 

84.  Compression.     See  also  II  146,  p  1198. 

A,  exclusive  of  temp  stresses, 

B,  including  stresses  due  to  temp  changes  of  40°  F 

In  arches  for  bridges,  Ibs  /  Q":  A 

for  highways  and  electric  railways 500  600 

for  steam  railways   .400  500 

85.  On  first-class  Port  cem  cone,  with  agg  properly  graded: 

1  :  6  or  less,  60,000  Ibs  /  sq  ft  = 417  Ibs  /  D"; 

1  :  5  or  less,  in  beams  or  slabs 500 

"In  case  a  richer  cone  is  used,  this  stress  may  be  increased  with  the  ap- 
proval of  the  commissioner  to  not  more  than"  600  Ibs  /  n",  Ms. 


*  s  =  ult  comp  strgth  in  Ibs  /  D"  at  28  days  when  tested,  under  labora- 
tory conditions,  in  the  form  of  cyls  8"  diam,  16"  long,  of  same  consistency  aa 
used  in  the  field. 

t  When  s  =  2000  Ibs  /  Q". 


1194  CONCRETE. 

For  lists  of  Specifications  for  Concrete,  see  pp   1184,  1185. 

86.  Portland,  1:2:4..  230  Ibs  /  FT 

,   1:2:5 '.'.'.'.'.'.208         " 

Rosendale  or  equal, 

1  :2:4 125 

1:2:5 Ill         "  N  Y.* 

87.  Portland,  Ibs  /  Q".         Mix,  1:2:4         1:2.5:5         1:3:6 

machine-mixed 400  350  300 

hand-mixed 350  300  250 

Natural 150 

Cinder,  700  ; 

Port,  in  reinfd  cone;  direct,  0.2  X  ult;  in  bending,  0.35  X  ult.  Oh. 

88.  Port,  direct,  350  Ibs  /  Q";    in  reinfd  work,  350  Ibs  /  G"  simultane- 
ously with  6000  Ibs  /  D"  tension  in  steel,  tin. 

89.  Port,  direct,  350;  in  bending,  500,  Mh. 

Aggregate 

90.  Port,  Stone  or  gravel     Slag  Cinder 

In  bending 600  400  250  Ibs  /  Q* 

Direct,  in  cols 

length  >  15  diam 500  300  150 

In  hooped  cols,  1000  Ibs  /  D"  on  area  within  hooping,  Ph. 

1:2:4  1:2:5  1:3:6 

Port 700  650  600  Ibs  /  D" 

Nat 400  ...  ...          "I* 

91.  Tension,  Ibs  /  D". 

A,  exclusive  of  temp  stresses, 

B,  including  stresses  due  to  temp  changes  of  40°  F. 

A  B 

In  reinforced  arches 50  75 

In  reinforced  slabs,  girders,  beams,  etc 0  0    OS. 

On  diagonal  plane,         0.02  X  ult  comp  strgth,  Oh.  ~~ 

92.  Shear.  Ibs  /  D". 

75,  CS ;  50,  Mh ;  60  when  uncombined  with  comp  upon  the  same  plane 
"unless  the  bldg  commissioner  with  the  consent  of  the  board  of  appeal 
shall  fix  some  other  value,"  Ms;  stone  or  gravel  cone,  75;  slag,  50;  cinder, 
25,  Ph. 

Elastic  modulus. 

93.  1,500,000  Ibs  /  D",  CS. 

Adhesion. 

94.  See  p  1111,  and  p  1196,  H  113. 

Safety  factors. 

or.     ,     ,  ultimate  load 

Safety  factor   =   -         -5-^ — T. 
allowed  load 

95.  At  end  of  1  mo,  in  subways  and  girder  bridges  for  highways  and 
electric  rys,  also  bldgs,  roofs,  culverts,  sewers,  4;  in  subways  and  girder 
bridges  for  steam  rys,  5,  OS. 

Port,  in  reinfd  cone,  comp,  direct,  5;  in  beams,  1/0.35;  Oh. 

In  reinfd  beams,  1  for  dead  load,  plus  4  for  live  load,  =  5; 

In  iron  or  steel  in  latticed  or  open  work  cols,  beams  or  girders,  encased  in 
cone  which  extends  <  2"  beyond  metal  (with  no  allowance  for  the  cone),  3 
It. 

Reinforcement. 

96.  Bars,  unpainted,  but  free  from  scale,  rust  and  grease,  €r. 

97.  Shape.     Plain    round    or    square,    or    corrugated,    I<v ;  plain  or 
twisted,  JTO  ;  deformed,  AH  ;  twisted  or  deformed,  Bu;  Square  machine- 

*  Corresponding  with  loads  proposed  by  C.  C.  Schneider,  Trans,  A  S  C  E, 
Vol  54,  Jun  '05,  p  384.  On  p  493  Mr.  Schneider  proposes,  instead,  for  Port 
cem  cone  only: 

per  sq  ft  per  sq  inch 

1:2:5 .20  tons  =  40,000  Ibs  278  Ibs. 

1:2:4 25     "     =50,000    "  347     ". 


CONCRETE  SPECIFICATIONS.  1195 

For  abbreviations,  symbols  and  references,  see  p  947  Z. 

twisted,  Co ;  Ransome  twisted  square  preferred,  F;  Ransome  or  equal, lib  ; 
Thacher  bar,  CS ;  square,  twisted  cold,  or  Johnson  corrugated  bar;  in 
Johnson  bar,  net  section  =  that  reqd,  by  the  plans,  for  twisted  bars;  plain 
bars  to  be  used  in  comp  only,  Ci. 

98.  Twisted  bars. 

Size,  ins    M     H      M       %        H      %         1          I^IM 

Twists  per  ft 12     8       5       3.5      2.5      2       1.75      1.5      1.5,    BT O,  Co ; 

6 1.5        Ci. 

One  turn  in  5  to  7  times  nominal  size,  F. 

Twisted  uniformly  by  machinery;  min  cross  sec  area  to  vary  not  more 
than  2.5  %,  WO,  €o. 

99.  Round,  corrugated,  etc,  bars  to  have  same  agg  net  sec  area 
as  square  or  twisted  bars,  WO. 

Requirements. 

100.  Iron  and  steel  "to  meet  the  'Manufacturers' Standard  Specfns,' 
revised  Feb  3,  '03,"  Ph.     See  pp  873  a,  b. 

101.  Steel.    Mfr  and  hardness.     Medium  open-hearth,  WO,  Bu, 
Co,  Ci ;  mild,  ItV ;  soft  or  medium,  CS. 

102.  Ultimate  tensile  strength,  in  thousands  of  Ibs  /  Q*.     52 
to  62,  F ;  54  to  64,  Un,  Mh :  medium,  50  to  65,  Ci,a ;  medium,  60  to 
68,  CS ;  soft,  54  to  62,  CS ;  55  to  65,  L,v,  TAT;   <  55,  WO ;  57  to  65, 
Co,a ;  60  to  70  before  twisting,  Co,b ;  60  to  70,  Bu. 

103.  t'li  comp  strength. 

Mixture  1:1:2     1:1.5:3     1:2:4     1:2.5:5     1:3:6 

Ibs/Q"  2900  2400         2000  1750  1500 

n   =   ES/EC  =  10  12  15  18  20 

Ch. 

104.  Fracture,  silky,  uniform  in  color  and  texture,  Co. 

105.  Elastic  limit  <  half  ult  tensile  strgth,  G. 

106.  Elastic  modulus,  30,000,000  Ibs/Q",  CS. 

107.  Ratio,  n,  of  elastic  moduli,    n  =  ~*  =  das  mod  for  steel 

Ec       elas  mod  for  cone 

n  =  12,  Mh.  "If  not  shown  by  direct  tests,"  in  beams  and  slabs,  re  =  15; 
in  cols,  n  =  10,  Ms;  with  ult  comp  strgth  =  2000  Ibs  /  Q",  n  =  18,  Un. 
Stone  or  gravel  cone,  n  =  12;  slag,  re  =  15,  Ph  ;  cinder,  re  =  30,  Ph,  Ch. 

108.  Elongation,  %,  minimum,  in  8",  25,  F,  L.V,  WO,  Co.a :  22, 

Co,b,  Ci,a;  20,  Un,  Mh;  soft,  25;  medium,  22,  CS ;      1>1P0t"00,,  ,  T  &  T. 

tensile  strgth 

109.  Bending  test.     Cold,  F,  I^v,  Bu,  CS ;  hot,  cold  or  quenched, 

NO,  Co,a;  180°  about  a  diam  =  the  thickness  of  the  bar,  F,  WO,  Bu, 
Co,  CS;  (before  deforming,  F);  about  a  diam  =  twice  the  thickness  of 
the  bar,  IiV ;  (after  deforming,  F) ;  soft  steel,  flat,  CS ;  cold,  90°  over  a 
diam  =  twice  the  thickness  of  the  bar  in  steel  >  %"  diam;  over  a  diam 
=  3  X  thickness  of  bar  in  steel  >  %"  diam,  Ch. 

Maximum  stresses  allowed  in  steel. 

Stresses  in  Ibs  /  Q"  unless  otherwise  stated. 

110.  Tension,  16,000,   Mh,  Ph,  .1C;   (iron,  12,000,  Ph);    one-third 
elas  lim,  but  not  over  18,000,  Ch ;  mild,  12,000;  medium,  15,000;  high 
carbon,  18,000,  L. 

111.  Shear,  10,000,  Mh ;  12,000,  Ch. 

.  .  elas  mod  in  steel    __ 

112.  Comp  =  comp  in  cone  X  -  — ,  Ch. 

elas  mod  in  cone 

"In  arches,  the  steel  ribs  under  a  stress  not  exceeding  18,000  Ibs  per  square 
inch  must  be  capable  of  taking  the  entire  bending  moment  of  the  arch  with- 
out aid  from  the  cone,  and  have  flange  areas  of  <  the  150th  part  of  the  total 
area  of  the  arch  at  crown.  The  actual  stress  when  imbedded  in  and  acting 
in  combination  with  cone  shall  not  exceed  20  times  the  allowed  stress  on 
the  cone." 

79 


1196  CONCRETE. 

For  lints  of  Specifications  for  Concrete,  see  pp  1184,   1185. 

"In  slabs,  girders,  beams,  floors,  and  walls,  subjected  to  transv  stress,  the 
steel  shall  be  assumed  to  take  the  entire  tensile  stress  without  aid  from  the 
cone,  and  shall  have  an  area  sufficient  to  equal  the  comp  strgth  of  cone 
composed  of  1  part  Port  cem,  3  parts  sand,  and  6  parts  of  broken  stone,  of 
the^  age  of  6  mos. " 

"In  walls  or  posts  subjected  to  comp  only,  no  allowance  will  be  made  for 
the  strgth  of  imbedded  steel,  which  will  be  used  only  as  a  precaution  against 
cracks  due  to  shrinkage  or  changes  of  temp." 

"In  tanks,  the  imbedded  steel  under  a  stress  not  exceeding  15,000  Ibs  /  Q" 
shall  be  capable  of  taking  the  entire  water  pres  without  aid  from  the  cone," 
Cfli» 

Elongation  in  service  not  more  than  0.2  %,  Ch. 

113.  Adhesion  between  steel  and  concrete.     Assumed  >  al- 
lowed shear  on  cone,  Mh,  Ms :   <  shear  on  cone,  Un ;  in  stone  or  gravel 
cone,  50  Ibs  /  Q";  slag,  40;  cinder,  15,  Ph. 

114.  In  1  :  2  :  4  cone,  max,  Ibs  /  D": 

on  plain  round  or  square  bars,  structural  steel 70 

high  carbon  steel 50 

on  plain  flat  bars,  ratio  of  sides  >  2  :  1 50 

on  twisted  bars,  <  1  twist  in  8  diams 80 

on  specially  formed  bars, 

0.25  X  ult  adhesion  as  determined  by  test;  max =   100      Ch. 

115.  When    the    allowed    adhesion  is  exceeded,   "provision 
must  be  made  for  transmitting  the  strgth  of  the  steel  to  the  cone,"  IJn,  Mh, 

116.  Length  and  lapping. 

Longitudinal  bars  not  less  than  3O  ft,  if  possible,  Lv. 
In  beams,  rods  of  single  length,  if  possible,  NO,  Co,  Ci. 
If  lapped 

Size  of  rod,  ins Y*    %     Yz    Ys     %      Ys       1     1YS     1H 

Lap,  ins 6     10     13     18     20     22     26     30       32  NO. 

6       9     12     15     18     20     22     24       27  Co. 

Lap  =  25  diams  of  rod,  Bu. 
Lap  <  20  X  diam  of  rod,  <  1  foot,  Ci. 
In  parallel  rods,  joints  staggered,  Bu,  Ci. 
Ends,  not  less  than  2"  from  any  surf,  Ly. 

Rods  extend  to  extreme  edges  of  unfinished  surfs. 

"  within  L"  of  finished  surfs.     Co. 

Floor  rods  extend  4"  beyond  face  of  wall  supporting  the  floor; 
Beam     "         "       <    8"   beyond   face   of    wall   supporting   the   floor, 
NO,  Ci.     See  Clearance,  below. 

117.  Protection.     If  work  is  interrupted,  bars,  already  placed,  must 
be  protected,  as  with  canvas  or  tarred  paper.     Ends,  projecting  for  a  con- 
siderable time,  to  be  painted  with  heavy  coat  of  neat  cem  grout,  F,  Lv. 

Permit. 

118.  Complete  detailed  plans  and  specfns,  giving  composition  of  cone,  to 
be  filed  with  the  Commissioner  of  Bldgs,  Ch,   Un,  Mh,  Ph. 

Issue  of  permit  does  not  involve  acceptance  of  constr,  Ch.  For  tests 
required,  see  pp  1194-5. 

Clearance.     See  also  HU  116,  134,  144,  149. 
instance,  t,  between  steel  and  surf  of  cone. 

119.  In  cols,  beams  and  girders,  t  <  1 1/2",  Ch,  Ms :    in  slabs, 
t  <  H"  <  diam  of  bar,  Ch ;  t  <   %",  Ms;  t  <  1.5  X  diam  of  bar,  JC. 

Axis  of  rods  dist  from  outside  of  cone  <  diam  of  rod,  CS. 
For  fireproof  buildings,  see  1J1f  120-128. 

Clear  dist  betw  bars  <  1.5  X  max  sectional  dimension  of  bar, 
Ch,  JC.  Clear  dist  betw  two  layers  of  bars,  <  %",  JC. 

120.  For  fireproof  buildings  (U1I  120-128),  reinfd  cone  constr  not 
approved  "unless  satisfactory  fire  and  water  tests  shall  have  been  made 
under  the  supervision  of  this  Bureau,"  Mh. 

May  be  accepted  if  designed  as  prescribed  in  code,  provided  that : 

(1)  Agg  shall  be  "hard -burned  broken  bricks,  or  terra-cotta,  clean  furnace 


CONCRETE   SPECIFICATIONS.  1197 

For  abbreviations,  symbols  and  references,  see  p  947  I. 

clinkers  entirely  free  of  combustible  matter,  clean  broken  stone,  or  furnace 
slag,  or  clean  gravel,  together  with  clean  siliceous  sand,  if  sand  is  reqd  to 
produce  a  close  and  dense  mixture  ; "  Un.  (The  other  codes  quoted  specify 
fewer  permissible  varieties  of  agg.)  Agg  to  pass  %  in  sq  mesh,  Ch  ;  1"  ring, 
and  25  %  of  agg  >  half  max  size,  Ph. 

(2)  Min  thickness,  t,  of  cone,  surrounding  the  reinfg  members,  shall  be 
as  follows,  where  d  =  diam  parallel  to  t : 

121.  When  d  >    W ,  t   =    1";  when  d  >    34",  t  =  4  d.     In  any  case    t 

>  4";  t  <  thickness  required  for  structural  purposes  plus  a,  a    =  1"  in  cols 
and  girders,  a  =    %"  in  floor  slabs  "but  this  shall  not  be  construed  as  in- 
creasing the  total  thickness  of  protecting  cone  as  herein  specified."     Un. 

122.  In  girders  and  columns,  t  =  2";  in  beams,  t=  1  W\  in  floor 
slabs,  t  =  l*i  JC. 

123.  In  monolithic  cols,  the  outer  1  Y^'  to  be  considered  as  protective 
covering,  and  not  included  in  effective  section,  JC. 

124.  For  beams  and  girders ;    on  bottom,  t  =  2";  on  sides,  t  = 
1  y/.     Under  slab  rods,  t  =  1".     In  cols,  t  =  2",  Ch,  Ph. 

125.  "If  a  supplementary  metal  fabric  is  placed  in  the  cone  surrounding 
the  reinfg,  simply  for  holding  the  cone,  the  thickness  of  cone  under  the  re- 
infg may  be  reduced  by  %",  such  fabric  shall  not  be  considered  as  reinforcg 
metal,"  €h. 

126.  On  floor  and  roof  beams,  t  =  1";  on  floor  and  roof  girders,  and  on 
beams  carrying  masonry,  on  top,  t  =  1";  elsewhere,  2";  on    cols,  carrying 
only  floors,  t  =  3";  on  cols  built  into  or  carrying  walls,  4",  Ms. 

127.  Cinder  concrete,  for  fireproof  constr,  t  same  as  for  stone  cone; 
for  slow-burning  or  mill  constr,  on  cols,  t  =  2";  "on  beams,  girders  and  other 
structural  steel  or  iron  members,"  t  =  1 M"-     Covering  to  have  "metal 
binders  or  wire  fabric  imbedded  in  and  around"  such  members;  binders, 
if  of  wire,  not  less  than  No.  8,  not  less  than  16"  apart,  Ch. 

128.  Corners  of  cols,  beams  and  girders,  to  be  beveled  or  rounded,  JC. 

Columns. 

129.  Columns  must  be  allowed  <   2  hrs  for  settlement  and  shrinkage 
before  girders  are  constructed  over  them,  JC. 

ISO.  "  Rules  for  the  computation  of  reinfd  cone  cols  may  be  formu- 
lated from  time  to  time  by  the  bldg  commissioner  with  the  approval 
of  the  board  of  appeal, "  Ms. 

131.  Concrete  and  steel  assumed  to  shorten   "in   the  same 
proportion",  Ms. 

132.  Cone  and  steel  stressed  in  ratio,  n,  of  their  elastic  moduli, 
JC. 

133.  Rods  tied  together  at  intervals  sufficiently  short  to  prevent 
buckling,  Ms.     See  1  136. 

134.  Outer  1  H"  to  be  considered  as  protective  covering  and  not  included 
in  effective  section,  JC. 

Reinforced  columns. 

L   =   length;  d  =  diameter  or  least  side. 

135.  Reinfd  cone  may  be  used  for  cols  when  L  >  12  d,  Ch,  Un,  Mh ; 

>  15  d,  JC;  and  where  cross  section  area  <  64  Q",  Ch.     If  L    >    15  d, 
allowable  stress  to  be  decreased  proportionally,  Ph. 

136.  Requirements.     Rods  to  be  tied  together   at  intervals 
not  more  than  d,  Un,  Mh,  Ph  ;  not  more  than  12  d,  not  more  than  18",  Ch. 
See  H  133. 

137.  Longitudinal    rods  not  considered  as  taking  direct  compres- 
sion, Ph. 

138.  Combined  cross  section  area  of  comp  rods  >  3  %  of  cross 
sec  area  of  col,  Ch. 

139.  When  comp  rods  are  not  reqd,  combined  cross  sec  area  of  rods  to 
be  <  0.5  %  of  cross  sec  area  of  col;  not  less  than  1  D",  Ch. 

140.  Least  dimension  of  smallest  rod  to  be  not  less  than  J^",  Ch. 


1198  CONCRETE. 

For  lists  of  Specifications  for  Concrete,  see  pp  1184,  1185. 

141.  Rods  to  extend  into  the  col  above  or  below,  lapping  the  rods  there 
sufficiently  to  develop  the  stress  in  the  rod  by  the  allowed  unit  for  adhesion, 
Ch. 

143.  Eccentric  or  transverse  loading.  Max  fiber  stress,  in- 
cluding (1)  direct  comp,  (2)  bending  due  to  direct  comp,  (3)  eccentricity 
and  (4)  transverse  load,  not  more  than  allowable  comp  stress.  Eccentric 
load  "shall  be  considered  to  affect  eccentrically  only  the  length  of  col  ex- 
tending to  the  next  point  below  at  which  the  col  is  held  securely  in  the 
direction  of  the  eccentricity,"  Ms. 

143.  A  column,  monolithic  with   or  rigidly  attached  to  a  beam 
or  girder,  must  resist,  in  addition  to  direct  loads,  a  moment  =   max 
unbalanced  moment  in  the  beam  or  girder  at  the  col,  Ch. 

144.  Hooped  columns.     Cone    may    be  stressed    to    25  %  of    ult 
itrgth,  provided 

(1)  Cross  sec  area  of  vert  reinfmt  <  area  of  spiral  reinfmt,  >  5  %  of 
area  within  hooping  ; 

(2)  Percentage  of  spiral  hooping  <  0.5,  >  1.5; 

(3)  Pitch  of  spiral  hooping  uniform  and  >  0.1  X  diam  of  col,  >  3"; 

(4)  Spirals  so  secured  to  verticals,  at  every  intersection,  as  to  main- 
tain form  and  position; 

(5)  Spacing  of  verticals  >  9",  >  H  circumference  of  col  within  hooping. 

Hooping  "may  be  assumed  to  increase  the  resistance  of  the  cone  equiv- 
alent to  2.5  X  the  amount  of  the  spiral  hooping  figured  as  vert  reinfmt." 
\Conc,  outside  of  hooping,  not  considered  as  part  of  effective  col  sec,  Ch. 

145.  "The  working  stresses  will  be  a  subject  for  special  consideration 
by  the  Commissioner  of  Bldgs,"  Un. 

146.  Allowed  unit  compression    =    1000  Ibs/D*  of  area  within 
hooping,  Ph. 

147.  Percentage  of  long'l  rods  and  spacing  of  hoops  to  be  such  that  the 
cone  may  develop  this  stress  with  a  safety  factor  of  4,  Ph. 

148.  "Hoops  or  bands  not  to  be  counted  upon  directly  as  adding  to  the 
strgth  of  the  col,"  JC. 

149.  Clear  spacing  of  bands  and  hoops  >  0.25  X  diam  of  enclosed  col,  JC. 

150.  Structural   steel   reinforced    columns.     Cone     may   be 
subjected  to,  M  ult  stress,  provided  (1)  cross  sec  area  of  steel  is  not  less  than 
1  D";  (2)  spacing  of  lacing  or  battens  not  more  than  least  width  of  col,  Ch. 

Beams  and  floors. 

151.  The  common   theory  of  beams  is   applicable.     In,  Ch, 

152.  The  steel  is  assumed  to  take  all  the  direct  tensile  stresses, 
X<,   I'll.  Ch,  Ms,  Mh,  Ph.     Tensile  stress  in  cone  to  be  considered  in 
calculating  deflections,  JC. 

153.  The  stress-stretch  curve  of  cone  in  comp  is  assumed  to  be  a 
straight  line,  Ch,  Ph.    n,  =  Ea/Ec  ,  =  15;  for  deflections,  n  =  8  to  12,  JC. 

154.  At  2000  lbs/D"  extreme  fiber  stress,  this  curve  may  be  taken  as 
(a)  a  straight  line;   (b)  a  parabola,  with  axis  vert,  and  vertex  on  neutral 
axis  of  beam;  or  (c)  an  empirical  curve,  enclosing  an  area  %  greater  than 
if  curve  were  a  straight  line,  and  with  cen  of  grav  at  same  height  as  that  of 
area  in  (b),  Uu. 

155.  Stresses.     A  load,    =   4   X   the  total  working  load,  stresses  the 
steel  to  its  elas  lim,  and  the  cone  to '2000  lbs/D",  Un.     Design  "based  on 
the  assumption  of  a  load  4  times  as  great  as  the  total  load,  Ph.      (Total 
load  =  ordinary  dead  load  plus  ordinary  live  load,  Un,  Ph.) 

156.  The  adhesion,  betw  cone  and  steel,  is  assumed  to  be  sufficient 
to  make  them  act  unitedly,  Un,  Ch,  Mh,  Ph. 

157.  Exposed  metal  not  considered  in  figuring  strgth,  Un,  Ch,  Ph. 

158.  Span    =   dist  c  to  c  of  bed   plates  or  other  bearings,  Ms,  JC. 
If  beam  is  fastened  to  side  of  a  col,  span  is  measured   to  cen  of  col,  Ms. 
Span  >  (clear  span  +  depth  of  beam  or  slab),  JC. 


CONCRETE  SPECIFICATIONS.  1199 

For  abbreviations,  symbols  and  re  ferences,  see  p  947  I. 

159.  Shrinkage  and  thermal  stresses  to   be  provided  for   by 
introduction  of  steel,  Ch,  Ph.     "Initial  stress  in  the  reinfmt,  due  to  con- 
traction or  expansion  in  the  cone,  may  be  neglected,"  JC. 

160.  When  the  shear  developed  exceeds  the  allowed  limit  for  cone, 
steel  must  be  introduced  to  take  the  excess,  Un,  Mh,  Ph,  JC. 

161.  Allowable  values  for  shearing  stresses:  Ibs/D" 

(a)  With  horizontal  bars  only 40; 

(b)  With  part  of  the  hor  reinfmt  in  the  form  of  bent-up  bars, 

"arranged  with  due  respect  to  the  shearing  stresses" >60; 

(c)  With  thoro  reinfmt  for  shear >120, 

Under  (c),  cone  may  be  taken  as  carrying  %  of  the  shear;  the  remaining 
%  being  carried  by  bent  rods  or  stirrups  (preferably  both)  carrying  their 
share  within  a  hor  dist  =  depth  of  beam,  JC. 

162.  Longitudinal  spacing  of  stirrups  or  bent  rods  >  0.75  X  depth  of 
beam,  JC. 

163.  Cement  finish,  added  to  the  tops  of  slabs,  beams  and  girders, 
not  to  be  included  in  figuring  strgth  "unless  laid  integrally  with  the 
rough  cone, "  and  to  be  allowed  no  greater  unit  stress  than  that  on  the  rough 
cone,  Ch. 

161.  Web  reinforcement.  "Where  the  vertical  shear,  measured 
on  the  sec  of  a  beam  or  girder,  betw  the  centers  of  action  of  the  hor  stresses, 

>  0.02    X    the  ult  direct  comp  stress /Q",  web  reinfmt  shall  be  supplied, 
sufficient  to  carry  the  excess.     The  web  reinfmt  shall  extend  from  top  to 
bottom  of  beam  and  loop  or  connect  to  the  hor  reinfmt.     The  hor  reinfmt, 
carrying  the  direct  stresses,  shall  not  be  considered  as  web  reinfmt,"  Ch. 

165.  Steel  in  the  compression  sides  of  beams  and  girders. 
"When  steel  is  used  in  the  comp  side  of  beams  and  girders,  the  rods  shall 
be  tied  in  accordance  with  requirements  of  vert  reinfd  cols  with  stirrups 
connecting  with  the  tension  rods  of  the  beams  or  girders,"  Ch. 

166.  "When  steel  or  iron  is  in  the  comp  sides  of  beams  the  proportion 
of  stress  taken  by  the  steel  or  iron  shall  be  in  the  ratio  of  the  mod  of  elas 
of  the  steel  or  iron  to  the  mod  of  elas  of  the  cone;  provided,  that  the  rods 
are  well  tied  with  stirrups  connecting  with  the  lower  rods  of  the  beams;" 
Ph. 

167.  Where  slabs  are   used    with   girders  and  beams,  the 
girders  and  beams  are  treated  as  T'-beams,  a  portion  of  the  slab  acting  as 
flange;  O. 

168.  Portion,  F,  of  width  of  slab,  acting-  as  flange. 
t   =  thickness  of  slab  ;  L  =  span  of  beam  or  girder  ; 

6  =  breadth  of  beam  or  girder  ;    S  =  dist  c  to  c  betw  beams  or  girders. 

F  to  be  "determined  by  assuming  that,  in  any  hor-plane  sec  of  the  flange, 
the  stresses  are  distributed  as  the  ordinates  of  a  parabola,  with  its  vertex 
in  the  stress-stretch  curve  and  with  its  axis  in  a  longitudinal  vert  plane  thru 
the  cen  of  the  rib  of  the  T."  Said  portion  to  be  reinforced  with  bars  near 
the  top,  at  right  angles  to  the  girder.  Un. 

169.  F  dependent  upon  hor  shearing  stress;   F  >  20 1,  Ph ;  F  >   10  b, 
Mil. 

170.  F  governed  by  shearing  resistce  betw  slab  and  rib;  F  >  S  (  1  —  j-2\ 

>  L/3,  >  %  S.     To  be  assumed  as  thus  acting,  slab  must  be  cast  at  same 
time  with  rib,  Ch. 

F  >  L/3,  >  -S,  Ms  ;    >  L/4,  >  8  t  +  b,  JC. 

171.  T  -beams  to  be  reinfd  against  shear  along  plane  of  junction  between 
rib  and  flange,  Un,  Ph  ;  using  stirrups  thruout  length  of  beam,  Ph. 

172.  Ribs  of  girders  and  beams  to  be  monolithic  with  floor  slabs. 
Un,  Ph. 

173.  "Where  reinfd  cone  girders  carry  reinfd  cone  beams,  the  portion  of 
the  floor  slab  acting  as  flange  to  the  girder  must  be  reinfd  with  bars  near 


1200  CONCRETE. 

For  lists  of  Specifications  for  Concrete,  see  pp  1184,  1185. 

the  top,  at  right  angles  to  the  girder,  to  enable  it  to  transmit  local  loads 
directly  to  the  girder  and  not  thru  the  beams,  thus  avoiding  an  integration 
of  comp  stresses  due  to  simultaneous  action  as  floor  slab  and  girder  flange." 

Un,  Ph. 

Moment,  M.     See  also  Iffl  178,  179. 

174.  W  =  load  per  sq  ft;    L  =  span,  in  ft.     In  freely  supported  slabs, 
L  =  free  opening  +  depth;   in  continuous  slabs,  L  =  distance  betw centers 
of  supports. 

175.  With  concentrated  or  special  loadings,  calculate  and  provide  for 
moments  and  shears  for  critical  condition  of  loading,  Ch. 

For  dead  load;  M  obtained  from  the  actual  dead  load")  covering  all 
'    live  load,  over  supports;  M  obtained  from  the        >-    spans  at 

actual  live  load  j  same  time. 

between  supports;  M    =   max  obtained  from  live  load 
covering  2  consecutive  or  2  alternate  spans  at  same  time. 
When  all  spans  are  equal,  let  M c  =   min  live-load  moment  at  middle  of 
span.     Then, 

W  L  2 
for  intermediate  spans,  M    = 


12 
W  L* 


for  end  spans MC  —  — 

W  L2 
Sum  of  live  load  moments  over  one  support  and  at  cen  of  span,  <  — - — , 

Ch. 

Continuity.     See  also  •  175. 

176.  Beams  and  girders  considered  as  simply  supported  at  ends  ; 
no  allowance  made  for  continuity,  Un,   51  h. 

177.  Beams,  etc,  calculated    as    simply    supported,    or    as    continuous, 
according  to  the  facts,  Ch,  Ms. 

178.  Continuous  floor   plates,  reinfd  at  top  over  supports,  may  be 
treated  as  oontinuous  beams.     Under  uniformly  distributed  loads,  mom,  M, 
taken  at  not  less  than  0.1  W  L;    0.05  W  L  with  square  floor  plates,  reinfd 
in  both  directions  and  supported  on  all  sides,  Un,  Mh,  Ph. 

179.  In  floor  slabs  adjoining:  walls;    if   slab    is    reinfd  in  one 
direction,  M  =      0     ;  if  square  and  reinfd  in  both  directions,  M  =  —.-£-; 

O  ID 

Ph. 

180.  Floor  slabs  designed  and  reinfd  as  continuous  over  the  supports. 
If  length  of  slab  >  1.5  X   its  width,  the  entire  load  should  be  carried  by 
transverse  reinfmt.     "Square  slabs  may  well  be  reinfd  in  both  directions," 
JC. 

181.  For  beams  and  slabs  continuous  for  >  2  spans,  bending  moms  at  cen 
and  at  support,  for  both  live  and  dead  loads,  as  follows: 

In  floor  slabs  and  in  interior  spans  of  continuous  beams,  M  =  w  L-/\2; 

in  end  spans  of  continuous  beams M  =  w  L2/10, 

w  =  load  per  unit  of  span;    L  =  span,  JC. 

183.  In  continuous  spans,  provide,  at  supports,  for 
negative  mom  =  0.8  positive  mom  at  cen  of  a  simply  supported  span. 

Pos  mom,  at  cen  of  continuous  span,  may  be  taken  =  neg  mom  at  support, 
Ms. 

Tests. 

183.  Bldg  Commissioner  may  require  tests  of  materials  before  or  after 
incorporated  into  bldg,  Ms.  Contractor  must  be  prepared  to  make  load 
tests  in  any  portion  of  bldg  within  a  reasonable  time  after  erection,  and  as 
often  as  may  be  reqd  by  engineer,  Ch,  Ph,  Mh,  Un.  Tests  must  show 
that  the  constr  will  sustain  loads  as  follows: 


SPECIFICATIONS   FOR   SIDEWALKS.  1201 

For  abbreviations,  symbols  and  references,  see  p  947 1. 

load  =  2  X  sum  of  proposed  dead  and  live  loads,  Ch ; 
=  2  X  proposed  live  load,  Ph ; 
=  3  X  proposed  load,  Mb. 

184.  Construction  may  be  considered  as  part  of  the  test  load,  Ch. 

185.  Each  test  load  shall  cover  2  or  more  panels,  and  remain  in  place 
not  less  than  24  hrs,  Ch. 

186.  Deflection  of  slabs  not  more  than  . 

oUU 


Deflection  of  girders  >  -~  '=•  X  ratio  of  slab  depth  to  girder  depth,  CJi. 

oUU 
187.  Test,  45  days  after  completion. 

Load  =  1.5  X  live  load  +  1.5  X  dead  load  of  finished  area. 
Deflection  >  0.001  X  length  of  member,  Ci,b. 

CONCRETE  SIDEWALKS. 

Abstract  of  Specification 

Adopted  by 
National  Association  of  Cement  Users 

Philadelphia,  January,  1908. 

1.  Cement,  Portland,  to  meet  specification  of  A  S  T  M,  adopted  Jan, 
1906.     See  p  940. 

2.  Sand.     To  pass  No.  4  screen.     May  contain  >  5  %  loam  and  clay, 
if  these  do  not  coat  the  sand  grains. 

<  60  %  of  the  sand  to  pass  No  10  sieve,  or 

35  %  to  pass  No  10  20  30  40  sieve, 
and  remain  on  No  20  30  40  50     "     ,  respectively. 
>  20  %  of  the  sand  to  pass  No  50  sieve,  or 

70  %  to  pass  No  10  20  sieve, 
and  remain  on  No  40  50     "     .respectively. 

3.  Screenings,  from  crushed  stone  as  below,  and  meeting  sand  require- 
ments, may  be  substituted  for  sand. 

4.  Aggregate.    Stone,    crushed    from   clean,   sound,   hard,   durable 
rock,  screened  dry  thru  %"  mesh,  retained  on  W  mesh. 

5.  Ciravel,    clean,    hard,   ranging    from   that   retained   on    W   mesh, 
to  that  passing  %"  mesh. 

6.  Unscreened  gravel,  clean,  hard.     No  particles  larger  than   %". 
Proportion  of  fine  and  coarse  particles  to  conform  to  requirements  below 
for  cone. 

7.  "Water,   "reasonably  clean,  free  from  oil,  sulfuric  acid  and  strong 
alkalies." 

Sub-base. 

8.  Sub-base  to  be   thoroly  rammed.     Soft    spots   removed   and 
replaced  by  hard  material. 

9.  Fills  >  1  ft  thick,  to  be  thoroly  compacted  by  flooding  and  tamping 
in  layers  >  6"  thick,  "and  shall  have  a  slope  of  <  1  :  1.5."     "The  top  of 
all  fills  shall  extend  <  12"  beyond  the  sidewalk." 

10.  "While  compacting,  the  sub -base  shall  be  thoroly  wetted  and 
shall  be  maintained  in  that  condition  until  the  cone  is  deposited." 

Base. 

11.  Voids.     Cem  must  overfill  voids  in  sand  by  <  5  %. 

12.  Mortar  must  overfill   voids  in  agg  by  <  10  %.     Proportions  1  :  >  8 
sand  and  agg. 

13.  When  the  voids  are  not    determined,   1  :  3  sand  or  screenings    :  5 
stone  or  gravel.     "A  sack  of  cem,  94  Ibs,  shall  be  considered  to  have  a 
vol  of  1  cu  ft." 

C12 


1 202  CONCRETE. 

Mixing. 

14.  Hand.     Sand  evenly  spread  on  a  level   water-tight  platform,  cem 
spread  on  sand.     Mix  dry  to  uniform  color.     Water  sprayed  and  mass 
turned   until   homogeneous   and    of   uniform   consistency.     Drenched    agg 
added  and  all  mixed  until  agg  is  thoroly  coated  with  mortar. 

15.  Hand.     With  unscreened  gravel.     Cem  and  gravel  "mixed 
dry   until   no   streaks   of  cem   are  visible."     Water  sprayed   and   mixed. 
Mortar  must  be  equivalent  to  that  specified  above. 

16.  Water  may  be  added  while  mixing,  but  cone  must  be  turned  < 
once  immediately  afterward. 

17.  "  Machine  mixing:  will  be  acceptable  when  a  cone  equivalent 
in  quality  to  that  specified  above  is  obtained. " 

18.  Retempering  prohibited. 

Grade. 

19.  Grade  of  sidewalk  <  sufficient  for  drainage,  >  W/ft,  "except 
where  such  rise  shall  parallel  the  length  of  the  walk." 

Forms. 

20.  Lumber,  clean,  free  from  warp,  <  1  %"  thick. 

21.  Upper  edges  to  conform  with  finished  grade  of  sidewalk. 

22.  Cross  forms.     "At  each  block  division,  cross  forms  shall  be  put 
in  the  full  width  of  the  walk  and  at  right  angles  to  the  side  forms, "  except 
as  in  U  23. 

23.  Expansion  joint.     A  metal  parting  strip  y?  thick  to  replace  a 
cross  form  <  once  in  50  ft.     "When  the  sidewalk  has  become  sufficiently 
hard,  this  parting  strip  shall  be  removed  and  the  joint  filled  with  suitable 
taaterial  prior  to  opening  the  walk  to  traffic.     Similar  joints  shall  be  pro- 
vided where  new  sidewalks  abut  curbing  or  other  artificial  stone  sidewalk." 

24.  "All  forms  shall  be  thoroly  wetted    before  any  material 
is  deposited  against  them." 

25.  dimensions  of  blocks. 

Size,  feet 6X6       5X5       4.5X4.5       4X4       3X3 

Thickness,  ins  : 

In  business  districts,  6  5.5  5  4  ... 

In  residence  districts,  6  5  ...  4  3 

In  residence  sidewalks,  edges  may  be  25  %  thinner  than  center;  min  =  3". 

26.  Separating  tool   >  6"  wide,  W  thick.     Groove  cut  thru  into 
sub-base;    groove  filled  with  dry  sand  before  the  top  coat  is  spread;    top 
coat  cut  thru  to  the  sand  after  floating  and  troweling,  "and  a  jointer  run 
in  the  groove";    trowel  then  drawn  thru  groove  again  "so  as  to  insure  a 
complete  separation  of  the  block." 

Depositing. 

27.  Cone  carried  to  forms   in  watertight  wheelbarrows.     Cone  must  not 
slop  over.     Barrows  must  not  be  run  over  freshly  laid  cone. 

28.  Cone  must  be  deposited  within  1  hour  after  mixing,  spread   evenly, 
and  tamped  until  water  flushes  to  the  top. 

Protection. 

29.  Workmen  must  not  walk  on  freshly  laid  cone. 

30.  Sand  or  dust,  collecting  on  the  base,  to  be  "carefully  removed  before 
the  wearing  surface  is  applied." 

Wearing  surface. 

31.  Minimum  thickness,  %". 

32.  Mortar,  1  :  2  sand  or  screenings,  mixed  as  for  base,  but  wet  enough 
not  to  require  tamping,  and  so  as  to  be  readily  floated  with  a  straight-edge. 
"A  thin  coat  of  mortar  shall  be  floated  on  to  the  base  before  spreading  the 
wearing  surf."     Mortar  spread  on  base  within  30  mins  after  mixing,  and 
floated  within  50  mins  after  base  cone  is  mixed. 


CONCRETE  BLOCKS.  1203 

33.  Marking.     "After  being  worked  to  an  approximately  true  surf, 
the  block  markings  shall  be  made  directly  over  the  joints  in  the  base  with  a 
tool  which  shall  cut  clear  through  to  the  base  and  completely  separate  the 
wearing  courses  of  adjacent  blocks." 

34.  Surface  edges  rounded  to  a  radius  <  W. 

35.  "When  partially  set,  the  surf  shall  be  troweled  smooth." 

36.  On  grades  >  5  %,  surf  to  be   roughened   by  a  suitable  tool  "or 
by  working  coarse  sand  or  screenings  into  the  surf." 

37.  Only  mineral  colors  shall  be  used,  and  these  shall  be  incor- 
porated with  the  entire  wearing  surf. 

Single  coat  work. 

38.  Proportions,  1  :  2  sand  :  4   gravel   or   crushed   stone.     Blocks 
separated  as  in  two-coat  work.     Cone  to  be  firmly  compacted  by  tamp- 
ing, and  evenly  struck  off  and  smoothed  to  the  top  of  the  mold. 
"Then,  with  a  suitably  grooved  tool,  the  coarser  particles  of  the  cone  tamped 
to  the  necessary  depth  so  as  to  finish  the  same  as  two-coat  work." 

Protection. 

39.  "When  completed,  the  sidewalk  shall  be  kept  moist  and  pro- 
tected from  traffic  and  the  elements  for  at  least  3  days.  The  forms  shall  be 
removed  with  great  care,  and  upon  their  removal  earth  shall  be  banked 

against  the  edges  of  the  walk." 

Grading  adjacent  to  sidewalk. 

40.  On  curb   side,  1  %"  below  sidewalk,  slope  <    W/ft.     On   property 
side,  "the  ground  should  be  graded  back  <  2  ft  and  not  lower  than  the  walk. " 


CONCRETE  BLOCKS. 

1.  Buffalo  harbor.     Blocks  6  ft  long,  abt  4  ft  sq,  88.75  cu  ft  =  3.3  CVL 

yds,  made  in  wooden  molds.  Yi  bbl  Port,  2.5  cu  ft  sand,  7.5  cu  ft  pebbles, 
7.5  cu  ft  broken  stone,  made  a  layer  of  cone,  in  mold,  about  6"  thick.  Faces, 
6"  thick,  of  blocks  on  lake-face  of  breakwater,  of  finer  material.  Face 
placed  first;  backing  placed  before  face  had  set.  (Emile  Low,  A  S  C  E, 
Trans,  June  '04,  Vol  LII,  p  96.) 

2.  Zeebrugge  breakwater,  Belgium.     Blocks  25  m  (82  ft)  long, 
9  m  (29.5  ft)  wide,  8.75  m  (28.7  ft)  high,  2000  cu  m  (2616  cu  yds),  4500 
tons  each.     Outer  cone  shell,  with  cutting  lower  edge,  three  compartments, 
formed  in  iron  framework  and  floated  to  place;    placed  between  guides  and 
block  last  sunk;    sunk  by  admission  of  water,  and  filled  up  with  cone, 
1  cem:  2.5  sand  :  6.1  broken  porphyry,  by  means  of  skips  of  10  cu  m  (13 
cu  yds).     Top  meter,  rich  in  cem,  placed  above  water  at  low  tide.     Seaward 
toe  immediately  protected  by  rubble  rip-rap. 

Superstructure  of  55-ton  blocks,  laid  above  water;    these  surmounted  by 
cone  blocks,  formed  in  place. 

3.  Molds  for   isolated   monolithic    sub-aqueous   concrete 
blocks,     from  150  to  222  cu  yds,  forming    pier  of    trapezoidal    cross- 
sec.     The  molds  are  bottomless  boxes  of    trapezoidal  cross-sec,  composed 
of  two  sides  and  two  end  pieces,  held  together  by  1  W'  turnbuckle  tie-rods 
acting  on  beams  placed  outside  of  the  mold.     The  tie  rods  have,  at  each 
end,  eyes  in  which  wedge-bolts  are  inserted  at  time  of  erection.     To  remove 
the  molds,  the  wedge-bolts  are  removed  by  turning  up  a  nut  on  the  rods 
which  form  an  integral  part  of  the  wedge-bolts.     This  pulls  the  wedge-bolt 
from  the  eyes  of  the  tie-rods  and  releases  the  walls  of  the  molds,  which 
are  then  picked  up  by  the  mold  traveller,  and  re-assembled  on  the  traveller 
ready  for  re-setting.     Weight  of  mold,  40  tons.     Time  reqd  for  removing 
mold  from  a  block  and  re- assembling  for  re-setting,  from  45  to  60  mins. 
Buoyancy  of  timber  overcome  by  cast  iron  ballast  wts.     Alternate  blocks 
placed  first.     For  intermediate  blocks  only  the  two  side  pieces  of  a  mold  are 
used.     These  are  held  in  place  and  at  their  proper  batter  by  six  turnbuckle 
tie-rods,  each  passing  thru  a  hollow  square  box  of  one-inch  plank,  acting 
as  a  strut.     (South  Pier  at  Superior  Entry,  Wisconsin.     Report  of  Clarence 
Coleman,  Asst.  Engr      Report  Chf  Engr,  USA,  1904,  Part  IV,  page  3781.) 


1204  CONCRETE. 

4.  "  Lewis  holes  should  be  cast  in  the  blocks  where  practicable" 
and  so  "as  not  to  bring  excessive  pres  on  the  cone,  particularly  near  the 
mortar  facing  or  near  the  arrises  of  the  block."     Lewises  and  dogs  may 
pull  out  of  green  blocks.     Provide  wooden  blocks  and  rag  cushions  for  use 
in  turning  over  the  blocks,  otherwise  the  corners  may  be  damaged. 

5.  Casting:  position.    Blocks  should  be  cast  with  the  most  important 
face  down,  their  showing  faces  as  nearly  vert  as  practicable,  and  the  back 
of  the  block  on  top,  so  that  laitance,  etc,  rising  to  the  surf,  may  appear  there. 

HOLLOW  CONCRETE   III  1 1  I>l \ «.   BLOCKS. 
Abstract  of  Specification 

Adopted  by 

National  Association  of  Cement  Users, 
Philadelphia,  January,  1908. 


1.  Cement,  Portland,  to  meet  specification  of  A  S  T  M,  adopted  Jan, 
1906.     See  p  940. 

2.  Sand,  silicious,  clean,  gritty,  to  pass   W  mesh  sieve. 

3.  Aggregate,  clean  broken  stone,  free  from  dust,  or  clean  screened 
gravel,  passing  %"  mesh  sieve,  refused  by  %" . 

4.  Unit  of  measurement  for  cem.     Bbl   =  380  Ibs  net;  cu  ft  > 
100  Ibs.     Cem  either  measd  in  original  package,  or  weighed;  not  measd 
loose  in  bulk. 

5.  Proportions.     For  exposed  exterior  or  bearing  walls. 

(a)  Machine-made.     Semi-wet,  1  :  >  3  sand  :  >  4  agg. 

(b)  Slush  (or  wet)  cone  (quaking  or  flowing),  made  in  individual  molds 
and  allowed  to  harden  in  them,  1  :  >  3  sand  :  >  5  agg. 

If  stone  is  omitted,  proportion  of  sand  may  be  increased  if  tests  show  no 
increase  in  voids  or  in  absorption,  and  no  loss  of  strength. 

6.  Water  enough  to  perfect  the  crystallization  of  the  cem. 

7.  Mixing:.  "Thoro  and  vigorous  mixing  is  of  the  utmost  importance. " 

(a)  Hand.     Cem  and  sand  mixt  dry.     Water  added  slowly  and  workt  in. 
Moistened  agg  spread  upon  mortar,  or  mortar  upon  agg.     Mix. 

(b)  Machine  preferred.     Cem  and  sand,  or  cem,  sand  and  agg,  mixt  dry. 
Water  added  and  workt  in.     With  wet  cone,  "this  procedure  may  be  varied 
with  the  consent  of  the  bureau,  etc." 

8.  Molding*.    Top  surf  of  tampt  blocks,  after  striking  off,  to  be  "trow- 
eled or  otherwise  finisht  to  secure  density  and  a  sharp  and  true  arris." 

9.  Curing-.     After  molding,  blocks  to  be    "carefully  protected    from 
wind  currents,  sunlight,  dry  heat  or  freezing  for  at  least  5  days,"  and  sup- 
plied with  additional  moisture  during  that  time  "and  occasionally  thereafter 
until  ready  for  use." 

10.  Minimum    ag-e  before    using.     1  :  3  sand,  3  weeks;   1  :  2    sand, 
2  weeks  "with  the  special  consent  of  the  bureau,  etc";  special  blocks,  for 
closures,  7  days  "with  the  special  consent  of  the  bureau,  etc." 

11.  Marking1.     All  blocks  to  be  markt  with  maker's  name  or  brand, 
day,  month  and  year  of  mfr,  and  proportions,  as  "1  :  2  :  3,"  etc. 

12.  Mortar.     "All  walls,  where  blocks  are  used,  shall  be  laid  up  with 
Portland  cem  mortar." 

13.  Maximum  load,  including  wt  of  wall,  8  tons  per  sq  ft  of  area 
of  blocks. 

14.  Thicknesses  of  walls.     Bearing   walls    "may    be    10%     less 
than  is  reqd  by  law  for  brick  walls."     In  curtain  or  partition  walls  same  as 
for  hollow  tile,  terra  cotta  or  plaster  blocks. 

15.  Offsets.  "Wherever  walls  are  decreased  in  thickness,  the  top  course 
of  the  thicker  wall  shall  afford  a  full  solid  bearing  for  the  webs  or  walls  of 
the  course  of  blocks  above." 

16.  Under  girders  or  Joists,  blocks  to  be  made  solid   for  <   8" 
from  inside  face.     If  concentrated  load,  W,  on  block,  >  2  tons,  this  applies 
to  the  blocks  supporting  the  girder,  etc;  if  W  >  5  tons,  it  applies  to  blocks 
for  <  3  courses  below,  and  to  a  dist  of  <  18"  each  side  of  girder,  etc. 


SPECIFICATIONS   FOR   BLOCKS.  1205 

17.  In  party  walls,  blocks  must  be  filled  solid. 

18.  Bond.  "Where  the  walls  are  made  entirely  of  cone  blocks,  but  where 
said  blocks  have  not  the  same  width  as  the  wall,  every  5th  course  shall 
extend  thru  the  wall,  forming  a  secure  bond,  when  not  otherwise  sufficiently 
bonded." 

19.  Block  facing-,  on  brick  backing,  "must  be  strongly  bonded  to  the 
brick,  either  with  headers  projecting  4"  into  the  brick  work,  every  4th  course 
being  a  header  course,  or  with  approved  ties,  no  brick  backing  to  be  less 
than  8"." 

20.  Thickness  of  web  of  block  (in  bearing  walls)  <  0.25  X  ht  of 
block. 

21.  Hollow  space.    In  bearing  walls,  min  percentage  of  hollow  space: 
Buildings  of  1st         2d          3d       4th        5th       6th  story 

1  &  2  stories 33         33 

3  &  4      "      25         33         33         33 

5  &  6      "      20         25         25         33         33         33 

22.  Sills  and  lintels  to  be  "reinforced  by  iron  or  steel  rods  in  a 
manner  satisfactory  to  the  bureau,  etc."     When  span  >  54",  lintel  "shall 
rest  on  block  solid  for  <  8"  from  face  next  the  opening  and  for  <  3  courses 
below  bottom  of  lintel." 

23.  Prior  to  use,  application  must  be  filed  with  bureau  or  with 
chief  of  proper  department,  giving  "a  description  of  the  material  and  a 
brief  outline  of  its  manufacture  and  proportions  used,"  with  "name  of  the 
firm  or  corporation,  and  the  responsible  officers  thereof,"  "and  changes  in 
same  thereafter  promptly  reported." 

24.  Certificate  of  approval  to  remain  in  force  >  4  mos,  "unless 
there  be  filed  with  the  bureau  of  building  inspection,  at  least  once  every  4 
mos  following,  a  certificate  from  some  reliable  physical  testing  laboratory 
showing  that  the  av  "  of  <  3  comp   tests  and  <  3   transverse  tests  comply 
with  requirements;  "the  said  samples  to  be  selected  by  a  building  inspector 
or  by  the  laboratory  from  blocks  actually  going  into  construction  work." 

25.  Preliminary  test.     Maker  to  submit  product  to  tests  required, 
and  file  certificate,  from  a  reliable  testing  laboratory,  giving  in  detail  the 
results  of  the  tests  made.    Results  of  all  tests,  satisfactory  or  otherwise,  t9  be 
filed  in  the  bureau,  open  to  inspection,  but  not  necessarily  for  publication. 

26.  Additional  tests.     Maker  or  user  or  both  "shall,  at  any  and  all 

times,  have  made  such  tests  of  the  cems  used  in  making  such  blocks,  or 
such  further  tests  of  the  completed  blocks,  or  of  each  of  these,  at  their  own 
expense  and  under  the  supervision  of  the  bureau  of  building  inspection,  as 
the  chief  of  said  bureau  may  require." 

Failure  to  stand  these  tests  involves  immediate  revocation  of  the  certifi- 
cate issued  to  maker. 

27.  Test  requirements.     Blocks  must  be  subjected  to  transverse, 
compression  and  absorption  tests,  "and  may  be  subjected  to  the  freezing 
and  fire  tests."     Freezing  and  fire  tests  not  at  cost  of  mfr. 

28.  Approval  tests  made  at  expense  of  applicant. 

29.  .\ot  less  than  12  samples  to  be  selected  by  bureau,  etc. 

30.  "Samples  must  represent  the  ordinary  commercial  product, 

of  the  regular  size  and  shape  used  in  construction.  The  samples  may  be 
tested  as  soon  as  desired  by  applicant  "  but  >  60  days  after  mfr. 

31.  Blocks,  failing;  to  stand  tests,  to  be  marked  "condemned" 
by  mfr  or  user,  and  destroyed. 

32.  "Tests  shall  be  made  in  series  of  at  least  3,  except  that  in  the  fire 
tests  a  series  of  2  (4  samples)  are  sufficient." 

33.  "  Half  samples  may  be  used  for  the  crushing,  freezing  and  fire 
tests.     The  remaining  samples  are  kept  in  reserve,  in  case  duplicate  or  con- 
firmatory tests  be  reqd." 


1206  CONCRETE. 

34.  "All  samples  must  be  marked  for  identification  and  com- 
parison." 

35.  Transverse  test.     Sample   (full  size)  placed   flatwise  on  parallel 
rounded  knife-edge   bearings,    7"   apart.     Load   applied,   midway   between 
supports,  thru  rounded  knife-edge. 

3  W  L 
Modulus  of  rupture  =  2;  where  W  =  load,  in  Ibs;  L  =  span  =  7"; 


6  =  breadth  of  block,  ins;  d  =  depth  of  block,  ins.  "No  allowance  should 
be  made.  .  .  for  the  hollow  spaces."  At  28  days,  modulus  of  rupture,  av  150 
lbs/D",  min  100. 

36.  Compression  test.     "Samples  must  be  cut  from  blocks,  so  as  to 
contain  a  full  web  section.     The  sample  must  be  carefully  measd,  then 
bedded  flatwise  in  plaster  of  paris,  to  secure  a  uniform  bearing  in  the  test- 
ing machine,  and  crushed.     The  total  breaking  load  is  then  divided  by  the 
area  in  compression  in  sq  ins,  no  deduction  to  be  made  for  hollow  spaces; 
the  area  will  be  considered  as  the  product  of  the  width  by  the  length." 

37.  Ultimate  comp  strength  at  28  days,  av  1000  Ibs/  D",  min  700. 

38.  For  bearing  walls,  min  1000  Ibs  /  Q".     No   deduction  to  be 
made  for  hollow  spaces. 

39.  Absorption.     Sample    dried    to   cpnstant    wt,    at     >     212°   F. 
Weighed;  placed  in  water,  face  downward,  immersed  <  2".     Weighed  at 
30  mins,  4  hours,  48  h,  and  replaced  in  water  immediately  after  each  weigh- 
ing.    At  end  of  48  h,  comp  strength  of  wet  specimen  to  be  determined  as 
in  U  36. 

wt  of  water  absorbed 

Absorption  =  —  —  .     Av  >  0.15;     max,  0.22. 

wt  of  dry  block 

40.  Reduction  of  comp  strength,  by  absorption,  >  %.* 

41.  Freezing  test.     Sample  immersed,  as  in  H  39,  for  <  4  h,  and 

weighed.  Subjected  to  <  15°  F  for  <  12  h.  1  h  in  water  of  <  150°  F. 
Operation  repeated  10  times.  Weigh  while  still  wet  from  lasf  thawing. 
"Its  crushing  strength  should  then  be  determined"  as  in  ^]  36. 

42.  Loss  of  weight,  max   10  %;  loss  of  strength,  max  %.* 

43.  Fire  test.     Two  samples  placed  in  cold  furnace.     Temp  gradually 
raised  to  1700°  F.     Maintained  for  <  30  mins.     One  sample  plunged  in 
water  of  about  50°  to  60°  F.     The  other  sample  cooled  gradually  in  air. 
"The  material  must  not  disintegrate." 

44.  Cement  brick,  as  substitute  for  clay  brick.     1  :  >  4  clean  sharp 
sand;  or  1  :  >  3  clean  sharp  sand  :  3  broken  stone  or  gravel  passing   Yi 
sieve  and  refused  by  W.    In  other  respects,  cem  bricks  to  conform  to  specfns 
for  hollow  cone  blocks. 

*  "Except  that,  when  the  lower  figure  is  still  above  1000  Ibs  /  D",  the  loss 
in  strength  may  be  neglected." 


COST.  1207 

COST. 

1.  The  following  data  respecting  prices  and  costs  are  compiled  from  rec- 
ords of  actual  cpnstruction  as  carried  out  by  men  presumably  skilled  in  the 
art,  and  employing  labor  at  ab9ut  the  usual  rates.     They  afford  only  approx 
estimates  of  what  may  ordinarily  be  expected.     The  cost  of  materials,  trans- 
portation, and  especially  of  labor,  varies  from  time  to  time  and  from  place 
to  place. 

2.  Not  only  does  the  rate  per  hour  for  labor  vary;  but  the  amt  of  work 
turned  out  in  a  given  time  varies  much  more  widely.     A  well  matcht  gang, 
presided  over  by  an  efficient  foreman,  will  produce  usually  from  two  to 
four  times  the  output  of  an  indifferent  gang.     Even  a  well-meaning  worker 
will  frequently  let  his  efficiency  drop  to  75  %  of  what  may  reasonably  be 
expected;  indifferent  workers  will  produce  only  30  or  20  %.     The  methods 
of  payment,  the  character  of  superintendence,  and  the  way  in  which  the 
work  is  arranged  and  handled,  are  all  very  important;  and  a  bungler,  or 
one  unfamiliar  with  cone  operations,  would  probably  find  difficulty  in  keep- 
ing the  total  costs  within  double  those  given. 

3.  The  principal  items,  making  up  the  cost  of  cone  (plain  and  reinfd) 
may  be  classified  as  follows: 

Materials;  Cem,  sand,  gravel,  stone,  reinfmt. 

Transportation  to  storage;  Hauling,  freight 

Storage. 

Screening,  washing. 

Mixing  ;  Loading  and  transporting  to  mixer,  mixing  machine  and  power, 
labor  and  depreciation  connected  with  it,  auxiliary  apparatus  as  mixing 
board,  barrows,,  shovels,  etc.,  and  transporting  cone  to  forms. 

Forms;  Erection,  shifting,  depreciation,  material,  labor. 

Depositing;  Dumping,  spreading  and  ramming. 

Finishing;  plastering,  brushing,  etc. 

Inspection  and  superintendence. 

Plant  (besides  mixer  and  forms);  Interest,  depreciation,  repairs,  insurance. 

Cost  of  Materials. 

4.  For  prices  of  cem,  sand,  etc,  see  "  Price  List,"  p  1211. 

5.  The  cost  of  any  one  material,  per  cu  yd  of  cone,  varies  greatly  in  diff 
cases,  due  to  wide  variations  in  the  percentages  employed  for  diff  grades  of 
cone,  and  can  therefore  be  approximated  only  betw  wide  limits. 

6.  Roughly  stated,  the  total  cost,  for  materials  alone,  may  be  ex- 
pected to  fall  somewhere  between  $2.50  and  $7.50/cu  yd  of  cone.     The  av 
would  probably  be  $4  or  a  little  more,  exclusive  of  reinfmt. 

7.  Cement.     For  prices,  see  "Price  List."  Per  cu  yd  of 
cone,  betw  $1.50  and  $4,  $2  and  $3  being  the  more  usual  limits;  affected 
chiefly  by  grade  of  cem  and  richness  of  mixture. 

8.  Sand.     For  prices,  see  "Price  List."  Per  cu  yd 
of  cone,  betw  15  cts  and  $1,  usually  below  25;  affected  chiefly  by  grade, 
dist  from  bank,  natural  monopoly,  and  proportion  used  in  mixture. 

9.  Oravel.    In  the  pit,  exclusive  of  screening,  loading  and  hauling,  from 
20  cts  to  75  cts  per  team  load;  affected  chiefly  by  quality,  and  natural 
monopoly. 

10.  Stone.     For  prices,  see  ' '  Price  List."  Av  price 
for  stone,  broken  to  reqd  size,  at  quarry,  exclusive  bf  cartage,  about  $1  or 
$1.50  /  cu  yd  stone.     Per  cu  yd  cone,  betw  50  cts  and  $1.     Affected  chiefly 
by  quality,  dist  from  quarry,  natural  monopoly,  and  proportion  of  mixture. 

11.  Reinforcement.     Cost  will  vary  with  the  design  and  type  em- 
ployed.    For  iron  and  steel  bars,  see  "Price  List." 

Plain  rods,  50  ton  lots,  at  mill,  cts  per  Ib,  approx: 

<  H",  ilA;      <W,1H;      <  SA",  2;      <  w,  2 1A. 

Ransome  twisted  rods,  about  *£  ct  per  Ib  more. 
Other  deformed  bars,  M  to  1A  ct  per  Ib  more. 

12.  The  percentage  of  reinfmt  usually  varies  from  about  ^  %  to 
of  the  cross-sec  of  a  beam  or  slab. 


1208  CONCRETE. 

Cost  of  Transportation  to  Storage. 

13.  Freight.     Cem,  by  rail.     Freight  rates  vary  greatly  in  diff  locali- 
ties, often  due  to  no  other  apparent  reason  than  arbitrary  discrimination, 
running  as  low  as  J^  ct  /  ton-mile,  and  above  2  cts;  in  general,  1  to  2  cts. 

14.  By  Canal.     Boat  loads  of  100  tons  of  2000  Ibs  each,  cem,  1  to  2  cts/ 
ton-mile,  according  to  dist;  stone  and  sand,    %  to  1  Y^. 

15.  Coastwise  freight.     In  carload  lots,  0.4  to  0.6  ct  /  ton-mile,  approx. 

Cost  of  Storage,  etc. 

16.  Storage.     Ordinary  cem  barrels  may  be  stored  about  5  layers  high, 
which  requires  about  1  M  Q  f  t  floor  space  per  bbl. 

17.  Screening.     Cost,   by  hand,    betw   10  and   25   cts  or  more  /  cu 
yd  of  material  handled.     Machine  screening,  betw  4  and  8  cts  /  cu  yd.     To 
obtain  the  cost  per  cu  yd  of  the  screened  material,  multiply  cost  per  cu 
yd  by  the  ratio  of  total  quantity  handled  to  quantity  accepted. 

18.  Washing.     Cost  of  washing  sand,  gravel  and  crusht  stone  may  be 
5  cts  or  more  /  cu  yd  of  material  handled,  for  mechanical  washers,  handling 
large  quantities.     For  small  quantities,  washt  under  unfavorable  condi- 
tions, as  high  as  40  cts. 

Cost  of  Mixing  and  Placing. 

19.  Mixing  and  placing.     Total  cost,  exclusive  of  forms,  from 
$1  to  $2.50  /  cu  yd  of  cone. 

20.  Labor  required,  for  fairly  large  quantities,  on  an  av,  one  man  i9r 
each  2  or  3  cu  yds  mixt  and  placed  per  day.     On  small  jobs,  each  man  will 
turn  out  much  less. 

21.  Dry  cone  costs  about  $1  more  per  cu  yd  to  mix  and  place  than  wet 
cone.     Herman  Conrow,  Jr,  A  S  C  E,  Trans,  Vol  42,  1899,  p  124. 

22.  Loading.     From  12  to  24  cu  yds  of  sand  loaded  into  carts  per  man 
per  day.     12  appears  to  be  usual,  but  24  not  unreasonable. 

23.  Transportation.     Av  load  broken  stone,  gravel  or  sand. 

Wooden  wheelbarrows 2M  to  21A  cu  ft  =  0.09  cu  yd. 

Iron  wheelbarrows 1.9  cu  ft  =  0.07  cu  yd. 

Cost  of  transportation  per  cu  yd  cone  ordinarily  betw  11  and  25  cts,  de- 
pendfing  largely  upon  the  length  of  haul  and  the  industry  of  the  laborers. 

Cost  of  Mixing. 

24.  Mixing  (only).     Much  depends  upon  the  diligence  of  the  laborers, 
and  the  size  of  the  mixer.     Several  examples  indicate  costs  less  than  10  cts 
/  cu  yd,  counting  labor  only,  while  others  indicate,  quite  regularly,  about 
25  cts.     Sabin  says  "The  cost  of  mixing  cone  in  large  quantities  is  seldom 
less  than  30  cts  /  cu  yd  if  allowance  is  made  for  plant." 

25.  As  far  as  practicable,  the  course  of  the  material  should  Be  downward ; 
the  mixer  being  kept  above  the  work  if  possible.     If  an  elevator  is  used 
for  the  cone,  its  entrance  should  be  below  the  mixer.     In  subway  or  sewer 
work,  the  mixer  can  sometimes  be  placed  below  the  street  level  and  yet 
above  the  level  of  the  work,  so  that  it  becomes  unnecessary  to  raise  the 
materials   again   after  dumping  them  onto   the   street   from   the  wagons. 
Much  may  be  lost  if  the  supply  of  materials  and  the  demand  for  cone  are 
not  kept  nearly  equal,  or  if  the  conditions  are  such  that  the  men  cannot 
keep  out  of  each  other's  way. 

26.  Ordinarily,  more  than  half  a  dozen  men  cannot  be  disposed  about  a 
mixer  to  operate  it  to  advantage,  measuring  materials,  cleaning  up  plat- 
forms, etc  (besides  those  actually  engaged  in  getting  the  materials  to  and 
from  the  mixer).     Cost,  for  labor  only,  should  not  be  much  over  15  cts  per 
cu  yd  of  cone,  even  with  small  machines. 

27.  Mixers,  turning  out  from  10  to  40  cu  ft  of  concrete  per  batch  (or, 
assuming  one  batch  every  2  mins,  10  to  40  cu  yds  per  hour)  will  cost  from 
$500  to  $1000,  and  will  require  from  5  to  10  HP.  to  operate.     Hand  power 
machines,  with  a  capacity  of  5  cu  ft  per  batch,  about  $250. 

28.  Cost  of  setting  np  a  mixer,  and  taking  it  down,  including  carting  a 
few  miles,  and  depreciation,  betw  $50  and  $100. 

Up  to  100  or  200  cu  yds  of  cone,  hand  mixing  is  usually  more  economical 
than  machine  mixing. 


COST.  1209 

29.  The  first  cost  of  a  hand  mixing  plant,  to  be  operated  by  8 
or  10  men,  estimated  as  follows: 

8  square-pointed  shovels,  size  No.  3 $10 

3  iron  wheelbarrows 35 

2  rammers 5 

1  mixing  platform,  15  X  15  ft 10 

Total $60 

30.  Performance.     When    material    is    promptly    delivered,  batch 
mixers  turn  out,  on  an  av,  one  batch  in  from  2  to  3  mins.     A  batch  in  one 
mm  is  extremely  fast  working.     Sometimes  4  or  5  mins  are  reqd.     For 
capacities  and  power  reqd,  see  under  "Mixers,"  ^  27. 

31.  The  cost  of  a  mixing  plant  for  cone  work  is  variously  estimated  at 
from  3  to  5  %  or  more  of  the  cost  of  the  work. 

32.  The  life  of  a  mixer,  unde-   av  conditions,  is  from  30,000  to 
40,000  batches.     Thus,   a  mixer,   turning  out   120  batches  per  day,   will 
require  renewal  in  about  a  year.     A  new  drum  will  generally  be  needed 
after  turning  out  two-thirds  the  total  quantity. 

33.  Mixer  to  forms.     Time  to  fill  a  barrow  from  a  mixer,  about  10 
sees;  to  discharge  the  entire  mixer  at  one  operation,  15  to  20  sees. 

34.  Av  barrow  load  of  mixt  cone,  1  ^  to  1  *£  cu  ft  =  0.06  cu  yd.     One- 
horse  carts  hold  about  %  cu  yd;  two-horse,  1  to  2  cu  yds.       To  compute 
costs  of  hauling,  etc.,  see  Art  4  under  "Cost  of  Earthwork,"  p  801. 

35.  About  10  or  15  cu  yds  of  cone  per  man  per  10  hour  day  can  be  loaded 
by  shoveling. 

Cost  of  Forms. 

38.  Cost,  including  material  and  labor,  varies  chiefly  with  the  character 
of  the  structure;  simple  forms  for  mass  work  being  relatively  cheap,  while 
those  for  detailing  walls  and  floors  of  bldgs,  especially  in  reinfd  cone,  are 
about  the  most  expensive. 

37.  Material  for  forms,  betw  10  and  80  cts  /  cu  yd  of  cone  in  place. 

38.  Fabrication  and  erection  will  cost  from  $4  to  $10  per  1OOO  ft  B.M. 
for  the  simpler  forms  of  construction;  in  buildings,  from  $10  to  $20. 

39.  The  cost  of  forms  may  be  as  low  as  10  and  as  high  as  50  per  cent  of 
the  total  cost  of  the  cone  in  place;  25  to  35  %  for  forms  for  ordinary  reinfd 
work,  50  %  or  over  for  detailed  building  worK. 

40.  The  cost,  per  sq  ft  of  surface  (as  one  side  of  a  wall)  can  be 
best  computed  for  the  work  in  hand,  given  the  cost  of  the  lumber  and  labor 
available;  but  will  usually  be  betw  4  cts  and  20  cts. 

41.  The  cost  of  forms,  per  en  yd  of  concrete,  in  building  constr, 
is  stated  betw  $3  and  $10,  from  $4  to  $6  being  sufficient  for  floor  construc- 
tion, and  $5  to  $7  being  more  usual  limits  for  forms  for  reinfd  work. 

42.  Shifting  and  depreciation.     The  figures    given    for    cost  of 
forms  assume  that  the  material  is  not  used  again.     For  special  work,  in- 
volving difficult  and  unusual  details,  the  forms  are  practically  worthless 
after  they  have  been  used.     Ordinarily  the  lumber  can  be  used  2  or  3  times 
before  it  is  discarded.     On  large  buildings,  the  forms  for  which  are  carefully 
designed,  and  where  the  detailing  is  similar  thruout,  forms  may  be  used  a 
half  dozen  times. 

43.  The  labor  of  shifting  forms  will  be  not  much  less  than  the  labor  of 
first  erecting  them. 

44.  Cost  of  labor,  for  placing-  forms,  betw  3  or  4  %  and  20  %  of  the 
cost  of  cone  in  place. 

Cost  of  Placing. 

45.  Cost    of    fabricating    (bending,   framing,   &c)    and    placing 

reinfmt,  from  about  3^  to  1  H  cts  /  Ib  of  reinfmt.     Unit  systems,  33  to 
50  %  more. 

46.  Depositing.  The  actual  labor  required,  for  depositing  only,  seldom 
amounts  to  more  than  an  extra  man  to  help  dump  carts,  move  shutes,  etc; 
not  more  than  a  few  cts  per  cu  yd  of  cone  placed.     Records  indicate  from 
7  cts  up,  but  these  probably  include  transportation  from  mixer  to  forms. 


1210  CONCRETE. 

47.  Spreading    and    ramming-.     Cost    varies    greatly    with    the 
character  of  the  work;  being  as  low  as  15  cts  /  cu  yd  in  fairly  rough  mass 
work  (5  cts  if    the    mixture    is  very  wet);    and    as    high  as  $1    or  more 
where  much  care  is  taken  in  placing,  tamping,  ramming  and  spading.     Less 
if  cone  is  dumpt  from  carts  or  buckets  in  large  quantities. 

48.  For  ramming  alone,  from  5  to  15  or  20  cts  /  cu  yd;  seldom  over  40  cts. 

Miscellaneous  €osts. 

49.  Inspection  and  superintendence,  as  usually  done,  about  1 
to  3  %  of  the  cost  of  the  work.     In  view  of  the  gross  inefficiencies  that  are 
likely  to  result  if  the  work  is  not  well  arranged  or  the  men  not  kept  up  to 
standard,  it  may  pay  to  expend  as  much  as  5  or  10  %  or  more. 

50.  Finishing^.     Data  very  variable,  due  probably  to  diff  in  method. 

51.  Washing  with  brush,  %  ct  to  7  cts  /  sq  ft  of  surf;  with  dilute  hy- 
drochloric acid,  to  remove  efflorescence,  about  20  cts  /  sq  ft. 

52.  Bush  hammering;  3  to  26  cts  /  sq  ft.     Pneumatic,  less  than  1  ct. 
Pointing  up  and  brush  coating,  25  cts  /  sq  ft  or  more. 

Total  Costs. 

53.  Plain.     For  total  costs,  see  "Mass,"  etc,  U  56. 

54.  Dry  cone,  about  $1  more  per  cu  yd  than  wet,  due  to  additional 
labor  of  ramming. 

55.  Gravel  cone    $1  to  $2  /  cu  yd  cheaper  than  stone  cone,  given  the 
same  ratio  of  (sand  +  stone)  to  cem,  the  greater  diff  obtaining  in  mixtures 
low  in  cem. 

56.  Mass.     Breakwaters,  fortifications,  etc,  cost  betw  $5  and  $7  /  cu 
yd  of  cone  in  place,  the  av  being  very  close  to  $6.     Extremes  as  low  as  $4 
and  as  high  as  $8. 

57.  Reinforced.     Where  work  is  well  organized,  reinfd  buildings  may 
be  built  for  as  low  as  $10  /  cu  yd  of  cone  in  place;  but  the  general  av  is 
nearer  $18,  while  some  builders  estimate  roughly  on  $1  /  cu  foot  ($27  /  cu 
yd)  altho  few  records  run  so  high. 

58.  The  cost  depends  chiefly  upon  the  forms  (see  "Forms,"  H  36).     If 
these  are  well  designed,  so  that  they  are  easily  shifted  and  can  be  used  re- 
peatedly, the  cost  is  low;  as  compared  with  special  jobs,  where  refinements 
in  designing  would  not  pay. 

59.  Retaining;  walls,  foundation  walls,  abutments,  locks,  piers,  etc, 
vary  greatly,  apparently  owing  to  the  widely  varying  difficulties  of  construc- 
tion likely  to  be  encountered.     The  extremes  run  from  $4  to  $16  /  cu  yd 
of  cone  in  place.     Quite  often,  however,  the  price  will  be  betw  $6  and  $9. 
Reinfd  walls  from  $3  to  $10  more. 

60.  Arches  of  moderate  span,  say  up  to  30  ft,  for  culvert  work,  etc, 
from  $5  to  $10  /  cu  yd. 

61.  Building^.     Cost  may  be  expected  to  fall  betw  $6  and  $12  /  cu  yd 
of  cone  in  place,  with  the  av  about  $8  for  plain,  and  $10  to  $15  or  $20  for 
reinfd  construction. 

62.  For  any  given  type  of   constr,  all  portions  of  a  building  (except 
foundations),  such  as  the  floors,  walls,  and  columns,  cost  practically  the 
same  per  cu  yd. 

63.  Mr.    L.   C.   Wason    (E    R,    '09,  Feb  27,  p  233)    gives,  as    cost  of 
buildings : 

$  per  cu  ft  of  space  enclosed  $  per  sq  ft  of  floor 

max  av  min  max  av  min 

Offices  and  stores 0.197  0.131  0.084  2.42  1.77  1.12 

Factories 0.129  0.102  0.060  1.70  1.34  0.90 

Garages..                     ..0.118  0.102  0.085  1.23 

Filters 0.333  0.233  0.134  3.82  2.43  1.04 

Storehouses 0.083  0.076  0.069  0.84  0.71  0.58 

Mills,  etc,  2d  class.... 0.1 22  0.069  0.045  1.51  0.90  0.54 


PRICE  LIST.  1301 


PRICE 

For  a  work  of  this  kind,  any  attempt  to  present  exact  or  even  closely  approxi- 
mate prices  would  be  useless.  We  aim  merely  to  give  indications  of  normal 
costs  or  of  the  ranges  of  costs.  In  general,  the  figures  given  represent  prices 
before  the  European  war,  and  not  the  speculative  and  transient  prices  which, 
in  some  cases,  have  since  prevailed.  They  are  intended  rather  for  the  guidance 
of  engineers  unfamiliar  with  concrete  work  than  for  those  specializing  in  it. 

No  firm  is  to  be  held  to  exactly  or  even  approximately  the  figures  given. 
For  actual  quotations,  apply  to  those  named  in  the  Business  Directory,  pp  1307 
&  1309,  as  indicated  by  the  numbers  immediately  below  each  title  of  the  Price 
List. 

Wood,  1.  11  ii»  l  MI.  Timber. 

Lumber,  in  dollars  per  1000  ft  board  mesure  (B  M): 
Spruce,  2"  X4"  to  2"  X10",  28  to  37. 
Long  leaf  yellow  pine,  32  to  50. 
Hemlock,  21  to  24.50. 

Stone. 

82,  92. 

The  following  prices  of  stone  and  earth  are  for  large  lots,  f.o.b.;  in  some  cases 
delivered  alongside  wharf. 

Sand,  $0.50  to  $1.00  per  cu  yd. 

Gravel,  about  $1.00  per  cu  yd. 

Crusht  or  broken  stone,  60  cts  per  cu  yd  and  upward,  in  some  places  as 
high  as  $2.00.  About  $1.00  is  usual. 

Slag  sand,  35  cts  per  ton. 

Broken  slag,  65  cts  per  ton. 

Val  de  Travers  Mastic  Blocks,  $25  per  ton. 

Val  de  Travers  crusht  and  comprest  all-rock  Asphalte  Paving  Slabs,  crated, 
$4.80  per  sq  meter. 


TOMKINS  COVE 
BALANCED  CONCRETE  AGGREGATE 

To  meet  the  latest  concrete  requirements  in  engineering  practice, 
the  Tomkins  Cove  Stone  Company  have  equipped  their  plant  to 
furnish  "Balanced  Concrete  Aggregate"  in  which  the  voids  are  filled 
with  washed  stone  screenings  and  sand  ready  for  use  by  adding  cement 
only.  Prepared  in  this  way,  concrete  is  denser,  cleaner,  stronger  and 
costs  less  for  cement,  labor,  transportation  and  inspection.  Sizes  do 
not  separate  in  transit  if  the  voids  are  filled  with  sharp  fines  and  if  the 
material  is  kept  damp. 

In  the  best  concrete  the  large  stone  voids  are  filled  with  small 
stone;  the  small  stone  voids  are  filled  with  screenings;  the  screening 
voids  are  filled  with  coarse,  clean,  sharp  stone-sand  and  the  coarse 
sand  voids  are  filled  with  clean  fine  sand, — every  particle,  large  and 
small,  being  coated  with  a  thin  skin  of  cement. 

Our  Complete  Concrete  Mixture,  or  any  other  specified  mixture 
of  sizes,  will  be  drawn  down  from  separate  bins,  mixed  on  the  loading 
belt  and  thence  conveyed  to  cars  or  boat. 

Correctness  of  mixture  can  easily  be  tested  at  work  with  a  set  of 
standard  graded  wire  screens. 

Additional  information  on  application,  to 

CALVIN  TOMKINS,  30  CHURCH  ST.,  NEW  YORK  CITY 
Telephone,  6196  Gortland 


1302  PRICE  LIST. 

Sand. 

67. 

Asphalt. 

73. 

Sheet  paving  Asphalt,  about  $15  per  ton  f.o.b.  refinery. 
See  also  "Val  de  Travers"  under  "Stone." 


Cement. 

1,  2,  3,  5,  6,  7,  9,  12,  13,  14,  15,  17,  18,  20,  22,  23,  24,  25,  26,  30,  31,  34,  35,  37,  41, 
42,  43,  44,  45,  46,  48,  52,  55,  58,  59,  61,  63,  64,  65,  69,  70,  71,  72,  75,  77,  78,  79, 
82,  84,  86,  87,  88,  90,  91,  93,  94,  96,  97,  99,  101,  102. 

Portland  cement,  about  $1.00  to  $1.80  per  bbl. 

Natural  (Rosendale)  cements;    about  $1  per  bbl. 

Lime.     Eastern  common—;  75  cts  to  $1.15  per  bbl  of  300  Ibs. 

Hydrated  lime,  $5  to  $6  per  2000  Ibs  at  mill. 

Hardeners,  Concrete — . 

32,  74. 

2\i  cts  to  3  cts  per  Ib. 

Forms,  Steel—. 

10,  36,  39,  40. 


Speed"  Portland  Cement 


Finely  ground ;  superior  strength ; 
light  color;  meets  the  require- 
ments of  the  most  careful  engineers. 


Write 


Louisville  Cement  Company 

Incorporated  Louisville,  Ky. 


ADVERTISEMENTS. 


1303 


Specif 

I 

and  be 


PHA 

SURE 


Q  PORTLAND  CEMENT^ 

V_/i    •»•      i      •  n     s*i          •    i    ~A> 


V  \lsTested  By  Chemists 


Send  for  a  free  copy  of  8o-page  illustrated  handbook 

"ALPHA  CEMENT;   HOW  TO  USE  IT" 

Also  Art  Envelope  T  containing  views  of  distinctive 
concrete  construction 

ALPHA  PORTLAND  CEMENT  CO. 

GENERAL  OFFICES:  EASTON,  PA. 

SALES  OFFICES: 

New  York,  Hudson  Terminal  Chicago,  Marquette  Building 

Boston,  Board  of  Trade  Buffalo,  Builders'  Exchange 

Philadelphia,  Harrison  Building  Baltimore,  Builders'  Exchange 

Pittsburgh,  Oliver  Building  Savannah,  National  Bank  Building 


1304 


PRICE  LIST. 


Reinforcement. 

10,  11,  16,  19,  29,  40,  49,  57,  62,  68,  89. 

Reinforcing  bars,  f.o.b.  warehouse,  %"•  2%  jets  per  lb.,  to 

Fire-Proofing. 

8,  16,  29. 

Mixers,  Concrete  —  . 

16,  21,  28,  51,  53,  54,  56,  66,  81,  83,  98. 


",  2%  cte  per  Ib. 


29. 
4,  53. 


Water-Proofing-. 
Concrete  Block  Machines. 


Special  Constructions. 

10,  11,  27,  60,  80. 

Composition  Floor  ("Sanitary"),  12  cts  per  sq  ft.,  %"  thick,  f.o.b.  Syracuse, 


N.  Y. 


95. 


REC'V'G  CAP., 
INCHES 

8X14 

9X16 
10X18 
12X24 
14X36 


Crushers. 


CAPACITY, 
TONS  PER  HOUK 
10  to  15 
12  to  18 
16  to  24 
24  to  40 
45  to  60 


H.  P. 

REQUIRED. 
10  to  12 
12  to  15 
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makes  the  Lightest  Roof  s  and  Floors 


It  is  a  solid  steel  sheet  with  dovetail  corrugations  which  are  in- 
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sheets.  Is  used  for  concrete  roofs,  floors,  stairs,  partitions,  etc. 
Easily  handled,  quickly  erected,  and  makes  a  weatherproof  roof  even 
before  the  concrete  is  applied.  Ask  for  catalog  H. 
THE  BROWN  HOISTING  MACHINERY  CO.,  Cleveland,  O. 


ADVERTISEMENTS.  1305 

Marion  Bar  Splicers 

Reinforcing  Couplings  as  Strong 
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Save  Steel.  Give  Continuous  Reinforcement 


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The  Marion  Malleable  Iron  Works 

Marion,  Indiana 


1306  ADVERTISEMENTS. 


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BUSINESS  DIRECTORY.  1307 

BUSINESS  DIRECTORY. 

(Referd  to,  from  Price-List,  pp  1301,  1302  &  1304.) 
*1.  JLtria  Portland  Cement  Co.;    Detroit,  Mich. 

2.  Allentown  Portland  Cement  Co.;    Allentown,  Pa. 

3.  Alpha  Portland  Cement  Co.;    Easton,  Pa. 

*4.  American  Hydraulic  Stone  Co.;    Concrete  Block  Machines;    Century 

Bldg.,  Denver,  Colo. 
5.  Ash  Grove  Lime  and  Portland  Cement  Co. ;  Grand  Ave.  Temple,  Kansas 

City,  Mo. 

*6.  Atlas  Portland  Cement  Co. ;   30  Broad  St.,  New  York,  N.Y.  Also  Boston; 
Philadelphia;    Des  Moines,  la.;   Chicago;    Minneapolis  and  St.  Louis. 
7.  Bath  Portland  Cement  Co.;   Newark,  N.  J. 

*8.  Berger  Mfg.  Co.;   Sheet  Metal  Products;   Canton,  O.     Also  New  York, 
Boston,    Philadelphia,    Minneapolis,    St.    Louis,    San   Francisco   and 
Chicago. 
9.  Best  Bros.  Keene's  Cement  Co.,  The — ;   Plaster  for  Concrete  Surfaces; 

Medicine  Lodge,  Kan. 
*10.  Blaw  Steel  Construction  Co.;    Steel  Forms  for  Concrete  Construction; 

Pittsburg,  Pa.     Also  New  York  and  Chicago. 

*11.  Brown  Hoisting  Machinery  Co. ;  Ferro-inclave  Construction ;  Cleveland, 
O.     Also  New  York,  Chicago,  Pittsburg,  San  Francisco  and  Montreal. 
*12.  Canada  Cement  Co.,   Ltd.;    Portland  Cement;    273  Craig  St.,  West, 
Montreal,  P.  Q.,  Canada. 

13.  Cape  Girardeau  Portland  Cement  Co.;   Cape  Girardeau,  Mo. 

14.  Castalia  Portland  Cement  Co.;   Publication  Bldg.,  Pittsburg,  Pa. 

15.  Cayuga  Cement  Corporation;    Portland  Point,  N.  Y. 

*16.  Chicago  Builders'  Specialties  Co.;    Concrete  Mixers  and  Contractors' 
Supplies;    450-470  Old  Colony  Bldg.,  Chicago,  III.     Also  New  York. 

17.  Clinchneld  Portland  Cement  Corporation;    Kingsport,  Tenn. 

18.  Colorado  Portland  Cement  Co.;    Denver,  Colo. 

19.  Concrete  Steel  Co.;    Reinforcing  Bars;   42  Broadway,  New  York,  N.  Y. 

20.  Continental  Portland  Cement  Co.;    St.  Louis,  Mo. 

21.  Contractor's  Machinery  Co.;    Concrete  Mixers;    125  llth  St.,  Keokuk, 

Iowa. 

22.  Coosa  Portland  Cement  Co.;    Ragland,  Ala. 

23.  Crescent  Portland  Cement  Co.;    Wampum,  Pa. 

24.  Dexter  Portland  Cement  Co.;    Nazareth,  Pa. 

*25.  Diamond  Portland  Cement  Co.;   Williamson  Bldg.,  Cleveland,  O. 

26.  Dixie  Portland  Cement  Co.;    Chattanooga,  Tenn. 

*27.  European  Asphalts  Corp.;   Val  de  Travers  naturally  impregnated  bitu- 
minous limestone  Mastic  Blocks,  etc.;  79  Tompkins  St.,  New  York. 
28.  Excelsior  Mixer  &  Machinery  Co. ;   Milwaukee,  Wis. 

*29.  General    Fireproofing   Co.;     Reinforcing   specialties;     Youngstown,    O. 
Also  New  York,  Boston,  Philadelphia,  Washington,  Chicago  and  London. 

30.  German-American  Portland  Cement  Works;    La  Salle,  111. 

31.  Giant  Portland  Cement  Co.;   603-610  Pennsylvania  Bldg.,  Philadelphia, 

Pa.     Also  New  York  and  Boston. 

*32.  Globe  Steel  Co.;    Concrete  Hardener;    Mansfield,  O. 
*33.  Goodyear  Tire  &  Rubber  Co. ;   Akron,  O. 

34.  Helderberg  Cement  Co.;    Albany,  N.  Y. 

35.  Hercules  Waterproof  Cement  Co.;  705  Mutual  Life  Bldg.,  Buffalo,  N.  Y. 
-*36.  Hotchkiss  Lock  Metal  Form  Co.;    Steel  Forms  for  Concrete  Construc- 
tions;  Binghamton,  N.  Y. 

37.  Huron  Portland  Cement  Co.;    1575  Ford  Bldg.,  Detroit,  Mich. 

38.  Hydraulic  Pressed  Steel  Co.,  The—;  3160  East  61st  St.,  Cleveland,  O. 

39.  Indiana  Concrete  Mold  Co.;    Steel  Forms  for  Sidewalks;    266  E.  River 

St.,  Peru,  Ind. 
*40.  Inland  Steel  Co.;    Reinforcing  Bars;   Chicago,  111. 

41.  International  Portland  Cement  Co.;    Spokane,  Wash. 

42.  lola  Portland  Cement  Co.;    lola,  Kan. 

43.  Iowa  Portland  Cement  Co.;    Des  Moines,  la. 
*44.  Ironton  Portland  Cement  Co.;    Ironton,  O. 

45.  Knickerbocker  Portland  Cement  Co.;   30  E.  42nd  St.,  New  York,  N.  Y. 

46.  Lawrence  Cement  Co. ;  Philadelphia  and  New  York. 

47.  Lehigh  Valley  Testing  Laboratory;    Allentown,  Pa. 

*  Names  indicated  by  asterisks  are  those  of  firms  which  have  favored  us 

with  verification  or  correction  of  their  listings. 

C13 


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170  Pages.    Frontispiece.     47  Diagrammatic  Plates.     15  Illustrative  Plates. 

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SUPERINTENDENCE 

By  F.  E.  KIDDER 
Part  I— Masons'  Work.    Ninth  Edition 

Revised  and  Rewritten  by  THOMAS  NOLAN,  University  of  Pennsylvania. 

Presents  the  latest  and  best  modern  practice  in  masonry  construction. 

966  Pages.    7x9  Inches.     628  Figs. 

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THE  HOLLOW  TILE  HOUSE 

By  FREDERICK  SQUIRES 

The  book  treats  on  the  construction  of  the  fireproof  home,  the  most  modern 

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BUSINESS  DIRECTORY.  1309 

*48.  Louisville  Cement  Co.;  Cements  and  Limes;  325  W.  Main  St.,  Louis- 
ville, Ky. 

*49.  Lukens,  Lewis  N.— ;  Reinforcement;  Real  Estate  Trust  Bldg.,  Phila- 
delphia, Pa. 

*50.  Marion  Malleable  Iron  Works;   Bar  Couplings;    Marion,  Ind. 

*51.  Marsh-Capron  Mfg.  Co.;  Mixers;  465  Old  Colony  Bldg.,  Chicago,  111. 

*52.  Michigan  Portland  Cement  Co.;    Chelsea,  Mich. 

*53.  Miles  Mfg.  Co.;   Concrete  Machinery;   Jackson,  Mich. 

54.  Milwaukee  Concrete  Mixer  Co.;   762  30th  St.,  Milwaukee,  Wis. 

55.  National  Lime  Manufacturers'  Association;   Oliver  Bldg.,  Pittsburg,  Pa. 

56.  National  Mixer  Co.;  300  6th  St.,  Oshkosh,  Wis. 

57.  National  Wire  Cloth  Co.;   Ties  for  Reinforcing  Bars;   Sandusky,  O. 

58.  Nazareth  Cement  Co.;   Nazareth,  Pa. 

59.  New  Egyptian  Portland  Cement  Co.;    Detroit,  Mich. 

*60.  New  England  Column  Clamp  Co.;   220  Devonshire  St.,  Boston,  Mass. 
61.  Newaygo  Portland  Cement  Co.;   Grand  Rapids,  Mich. 
*62.  North  Western  Expanded  Metal  Co.;   Reinforcement;   Chicago,  111. 
*63.  Northwestern  States  Portland  Cement  Co.;    Mason  City,  la. 

64.  Ogden  Portland  Cement  Co.;    Ogden,  Utah. 

65.  Oklahoma  Portland  Cement  Co.;    Ada,  Okla. 

66.  Olsen  Concrete  Mixer  Co.;   302  Olsen  St.,  Elkhorn,  Wis. 

67.  Ottawa  Silica  Co.;    White  Sand  for  Facing  Concrete,  etc.;    Ottawa,  111. 
*68.  Page  Woven  Wire  Fence  Co.;   Reinforcement;    Monessen,  Pa. 

69.  Peerless  Portland  Cement  Co. ;    Union  City,  Mich. 

70.  Peninsular  Portland  Cement  Co.;   Jackson,  Mich. 

71.  Penn-Allen  Cement  Co.;   Allentown,  Pa. 

72.  Phoenix  Portland  Cement  Co.;    Nazareth,  Pa. 

73.  Pioneer  Asphalt  Co.,  The — ;   Lawrenceville,  111. 

*74.  Pittsburg  Crushed  Steel  Co.;    Concrete  Floor  Hardener  and  Facing; 

A.  V.  R.  R.  &  61st  St.,  Pittsburg,  Pa. 
75.  Portland  Cement  Co.  of  Utah;   Salt  Lake  City,  Utah. 
*76.  Sackett  Screen  &  Chute  Co.,    H.  B. — ;    Industrial  Cars  and  Track, 

Screens  and  Elevators;    1679-1691  Elston  Ave.,  Chicago,  111. 

77.  St.  Mary's  Cement,  Ltd.;    Toronto,  Canada. 

78.  San  Antonio  Portland  Cement  Co.;    San  Antonio,  Texas. 

*79.  Sandusky  Portland  Cement  Co.;  Waterproof  Compound,  Portland  Ce- 
ment, White  Portland  Cement;  Cleveland,  O. 

*80.  Sanitary  Composition  Floor  Co.,  Inc.;    120  Plum  St.,  Syracuse,  N.  Y. 

*81.  Schaefer  Manufacturing  Co.;    Concrete  Mixers;    Berlin,  Wis. 

*82.  Security  Cement  and  Lime  Co.;  Portland  Cement,  Hydrated  Lime; 
Hagerstown,  Md.  Also  Washington,  Baltimore  and  Pittsburg. 

*83.  Smith  Co.,  T.  L.— ;   Mixers;    1149  32d  St.,  Milwaukee,  Wis. 

84.  Southwestern  Portland  Cement  Co.;    El  Paso,  Texas. 

85.  Spackman  Engineering  Co.,  Henry  S. — ;  Concrete  and  Cement  Testing; 

2024  Arch  St.,  Philadelphia,  Pa. 

86.  Standard  Portland  Cement  Co. ;    Charleston,  S.  C. 

87.  Standard  Portland  Cement  Corporation;   San  Francisco,  Calif. 

88.  Superior  Portland  Cement  Co.;    Cincinnati,  O. 

89.  Sykes  Metal  Lath  and  Roofing  Co.;   Lead  Coated  Metal  Lath;  500  Wal- 

nut St.,  Warren,  O. 

90.  Texas  Portland  Cement  Co.;    Cement,  Texas. 

91.  Tidewater  Portland  Cement  Co.;    Baltimore,  Md. 

*92.  Tompkins,  Calvin — ;   Plaster,  Crushed  Stone,  Brick,  Aggregates  graded 

at  Quarry;   30  Church  St.,  New  York,  N.  Y. 
93.  Trinity  Portland  Cement  Co.;    Dallas,  Texas. 
*94.  United  States  Portland  Cement  Co.;   Coors  BMg.,  Denver,  Colo. 
*95.  Universal  Road  Machinery  Co. ;   Crushers,  etc. ;   Kingston,  N.  Y. 

96.  Virginia  Portland  Cement  Co.;    Fordwick,  Va. 

97.  Wabash  Portland  Cement  Co.;    Ford  Bldg.,  Detroit,  Mich. 

98.  Wege  Concrete  Machinery  Co.,  E. — ;  118  S.  Second  St.,  La  Crosse,  Wis. 

99.  Western  States  Portland  Cement  Co.;    Independence,  Kan. 

*100.  Westmoreland  Chemical  and  Color  Co.;    Oxides  of  Iron  and  Venetian 
Reds;    925  Chestnut  St.,  Philadelphia,  Pa. 

101.  Wolverine  Portland  Cement  Co.;  Coldwater,  Mich. 

102.  Wyandotte  Portland  Cement  Co.;    1575  Ford  Bldg.,  Detroit,  Mich. 

*  Names  indicated  by  asterisks  are  those  of  firms  which  have  favored  us 
with  verification  or  correction  of  their  listings. 


1310  ADVERTISEMENTS. 


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BIBLIOGRAPHY.  1311 

BIBLIOGRAPHY. 

The  following  list  of  books  makes  no  pretensions  to  completeness.     It  aims 
simply  to  be  usefully  suggestiv  to  the  general  civil  engineer. 

Abbreviations. 
AC        Archibald  Constable  &  Co.,   Ltd.,   10  Orange  St.,    Leicester  Square, 

London,  W.  C. 

CH        Chapman  &  Hall,  Ltd.,  11  Henrietta  St.,  Covent  Garden,  London,  W.  C. 
CL        Crosby,  Lockwood  &  Son,  5  Broadway,  Westminster,  London,  S.  W. 
LG        Longmans,  Green  &  Co.,  Fourth  Ave.  and  30th  St.,  New  York,  N.  Y. 
MC        The  Myron  C.  Clark  Publishing  Co.,  608  S.  Dearborn  St.,  Chicago,  111. 
McG     McGraw-Hill  Book  Co.,  Inc.,  239  W.  39th  St.,  New  York,  N.  Y. 
S  E.  &  F.  N.  Spon,  Ltd.,  57  Hay  market,  London,  S.  W.,  England.       - 

VN        D.  Van  Nostrand  Co.,  23  Murray  St.,  New  York,  N.  Y. 
W          John  Wiley  &  Sons,  Inc.,  432  Fourth  Ave.,  New  York,  N.  Y. 

Strength  of  Materials. 

*American  Society  for  Testing  Materials.  Index  to  "Proceedings,"  1898  to 
1912.  Am.  Soc.  for  Testing  Materials,  University  of  Pennsylvania, 
Philadelphia,  Pa. 

*American  Society  for  Testing  Materials.  Year  Book.  500  pp.  6X9.  Cloth. 
1914.  Am.  Soc.  for  Testing  Materials,  University  of  Pennsylvania, 
Philadelphia,  Pa. 

Bovey,  Henry  T. — .  Strength  of  Materials  and  Theory  of  Structures.  4th 
Ed.,  rewritten  and  enlarged.  981  pp.  943  figs.  8vo.  Cloth.  $7.50. 
1907.  W. 

Burr,  Wm.  H. — .  The  Elasticity  and  Resistance  of  the  Materials  of  Engin- 
eering. 6th  Ed.,  rewritten  and  enlarged.  1100pp.  8vo.  Cloth.  $7.50. 

1904.  McG;  W. 

Fuller,   Charles  E. — ,   and  Johnston,   William  A. — .     Applied  Mechanics. 

Vol.  II.     Strength  of  Materials.     W. 
Hatt,  William  Kendrick — ,  and  Scofield,  H.  H. — .     Laboratory  Manual  of 

Testing  Materials.     135  pp.     28  ills.     7%  X5M-     Cloth.     $1.25.     1913. 

McG. 
international   Association  for  Testing   Materials.     (Foreign  papers,   etc., 

have  been  translated  into  English.)     Proceedings  of  the  Sixth  Congress, 

New  York,  1912.     2vols.     2200pp.      Ill'd.     6X9.      Cloth,  $8.00;  paper, 

$7.00.     McG,  S. 
Kent,  William—.     Strength  of  Materials.     2d  Ed.     18mo.     Boards.     $0.50. 

1905.  VN. 

Kidwell,  Edgar—,  and  Moore,  Carlton  F.— .     Tables  of  Safe  Loads.     57  pp. 

6X9.     Paper.     $0.50.     McG. 
*Merriman,  Mansfield — .      Strength  of  Materials.      6th  Ed.,    revised  and 

enlarged.     16th    thousand.     179    pp.     54    figs.     5X7^-     Cloth.     $1.00. 

1912.     W,  CH. 
Morley,    Arthur—.     Strength    of    Materials.     3d  Ed.     506    pp.     244    ills. 

6X9.     Cloth.     $2.50.     LG. 
Murdock,  H.  E. — .      Strength  of  Materials.      2d  Ed.,  revised  and  enlarged. 

367pp.     156  ills.     5X7^.     Cloth.     $2.00.     1914.     W,  CH. 
*Unwin,  William  Cawthorne — .     The  Testing  of  Materials  of  Construction. 

3d  Ed.     490pp.     206  ills.     5  plates.     5^X8^.     Cloth.     $5.00.     1910. 
Winslow,  Benj.  E. — .     Tables  and  Diagrams  for  Calculating  the  Strength 

of  Beams  and  Columns.     53  pp.     19  full-page  plates.     12  X9,  oblong. 

Cloth.     $2.00.     McG. 
Wood,  De  Volson — .     A  Treatise  on  the  Resistance  of  Materials.     328  pp. 

129  figs.     8vo.     Cloth.     $2.00.     1904.     McG,  W. 

Concrete  and  Reinforced  Concrete. 

Andrews,  E.  S. — .     Elementary  Principles  of  Reinforced  Concrete  Construc- 
tion.    210pp.     57  ills.     5X7^.     Cloth.     $1.25. 
Ballinger,  Walter  F. — ,  and  Perrot,  Emile  G. — .     Inspector's  Handbook  of 

Reinforced  Concrete.     72  pp.     6  folding  plates.     4%  X7.     Flex,  leather. 

$1.00.     1909.     AC,  McG. 
Brooks,  John  P. — .     Reinforced  Concrete.     230  pp.     87  figs.     6  X9.     Cloth. 

$2.00.     1911.     McG. 
Buel,  Albert  W.— ,  and  Hill,  Charles  S.— .      Reinforced  Concrete.      2d  Ed.t 

revised  and  enlarged.     512pp.     357  ills.     8  plates;  tables;     6X9.     Cloth. 

$5.00.     1906.     McG. 

*     **  Belie vd  to  be  specially  useful. 


1312  ADVERTISEMENTS. 


A  combination  of  Cement  Age,  ot  New  York, 

Concrete,  Detroit, 
and  Concrete  Engineering,  Cleveland 


CONCRETE  is  a  Monthly  Magazine. 

It  is  for  the  man  who  designs  or  speci- 
fies concrete  —  who  builds  with  it — who 
superintends  concrete  construction  —  for 
every  practical  man  who  has  anything  to 
do  with  concrete.  It  covers  engineering 
practice,  architectural  development,  con- 
struction methods.  It  is  written  by  men 
who  know — is  the  product  of  practical 
experience — it  gets  at  the  nub  of  the 
matter — It  Tells  How.  It  is  more  than  a 
monthly  magazine.  It  is  an  Institution, 
bent  on  the  solution  of  your  individual 
problems.  The  yearly  subscription  price 
is  a  trifle  measured  by  its  earning  power 
in  dollars.  $1.50  for  twelve  months  in 
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ada; $1.00  more  to  foreign  countries. 
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Concrete- Cement  Age  Publish- 

Detroit         ing  Company        Michigan 


BIBLIOGRAPHY.  1313 

Concrete,  etc.,  Cont'd. 

Cochran,  Jerome — .  Reinforced  Concrete  Field  Handbook.  133  pp.  27 
ills.  Tables.  3^X5%.  Leather.  $1.00.  1915.  Concrete-Cement  Age 
Pub.  Co.,  310  New  Telegraph  Bldg.,  Detroit,  Mich. 

*Considere,  A. — .  Reinforced  Concrete.  Translated  by  Leon  S.  Moisseiff. 
2nd  Ed.,  enlarged.  242  pp.  32  figs.  $2.00.  1907.  McG. 

Dodge,  G.  F. — .  Diagrams  for  Designing  Reinforced  Concrete  Structures. 
112  pp.;  43  diagrams.  14^X12%.  Boards.  $4.00.  MC,  S. 

*Eddy,  Henry  T. — ,  and  Turner,  C.  A.  P. — .  Concrete-Steel  Construction. 
Parti;  Buildings.  438pp.  99  ills.  6^X9.  Cloth.  $20.00.  C.  A. 
P.  Turner,  Minneapolis,  Minn. 

*Gilbreth,  Frank  B.— .  Concrete  System.  184  pp.  220  ills.  10  folding 
plates.  8^X11.  Flex.  mor.  $5.00.  AC,  McG,  W. 

Gillette,  Halbert  P.—,  and  Hill,  Charles  S.— .  Concrete  Construction,  Meth- 
ods and  Cost.  700  pp.  310  ills.  Cloth.  $5.00.  1908.  MC. 

Hill,  Charles  S. — .  Concrete  Inspection.  187  pp.  15  ills.  3^X6^- 
Cloth.  $1.00.  1909.  MC,  S. 

Hool,  George  A. — .     Reinforced  Concrete  Construction. 

Vol.  I;  Fundamental  Principles.     254pp.     88  ills.     6^  X9M-     Cloth. 

$2.50.     1912. 

Vol.  II;  Retaining  Walls  and  Buildings.      675  pp.      412  ills.       34  plates, 
etc.  -  6  X9.     Cloth.     $5.00.     1913.     McG. 

Marsh,  Charles  F. — .  A  Concise  Treatise  on  Reinforced  Concrete.  233  pp. 
67  ills.  5^X8%.  Cloth.  $2.50.  1910.  VN,  AC. 

Marsh,  Charles  F. — ,  and  Dunn,  William — .  Manual  of  Reinforced  Con- 
crete, and  Concrete  Block  Construction.  290  pp.  113  ills.  52  tables. 
4X6^.  Flex,  leather.  $2.50.  1910.  VN. 

McCullough,  Ernest — .  Reinforced  Concrete;  A  manual  of  Practice.  136 
pp.  28  ills.,  and  frontispiece.  5X8.  $1.50.  1908.  Cement  Era  Pub- 
lishing Co.,  Chicago,  111. 

Mensch,  L.  J. — .  Architects'  and  Engineers'  Handbook  of  Reinforced  Con- 
crete Construction.  217  pp.  172  ills.,  many  tables.  $2.00.  1904. 

*M6rsch,  Emil— .  Translated  by  E.  P.  Goodrich.  Concrete  Steel  Con- 
struction. 3rd  German  Ed.,  1908,  revised  and  enlarged.  Over  400  pp. 
350  ills.  45  tables.  2  inserts.  7^X10.  Buckram.  $5.00.  1909.  AC,  McG. 

Potter,  Thomas — .  Concrete:  Its  Uses  in  Building.  3d  Ed.,  revised  and 
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Reid,  Homer  A. — .  Concrete  and  Reinforced  Concrete  Construction.  906 
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Rings,  Frederick — .  Reinforced  Concrete  in  Theory  and  Practice.  200  pp. 
203  ills.  5M  X8.  $2.50.  1910. 

*Sabin,  Louis  Carlton — .  Cement  and  Concrete.  2d  Ed.,  revised  and 
enlarged.  665  pp.  Ill'd.  161  tables.  $5.00.  1907.  McG. 

Sutcliffe,  G.  L. — .  Concrete:  Its  Nature  and  Uses.  2nd  Ed.,  revised  and 
enlarged.  396  pp.  Ill'd.  12mo.  Cloth.  $3.50.  CL. 

Taylor,  Frederick  W. — ,  and  Thompson,  Sanford,  E. — .  Concrete  Costs. 
1st  Ed.  731pp.  82  figs.  166  tables.  5J^  X8.  Cloth.  $5.00.  1912.  W,  CH. 

**Taylor,  Frederick  W. — ,  and  Thompson,  Sanford  E. — .  A  Treatise  on 
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253  ills.  6X9.  Cloth.  $5.00.  1911.  W,  CH. 

Trautwine  Jr.,  John  C. — ,  and  Trautwine  3d,  John  C. — .  Concrete.  Re- 
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pany, 257  S.  4th  St.,  Philadelphia,  Pa. 

**Turneaure,  F.  E. — ,  and  Maurer,  E.  R. — .  Principles  of  Reinforced  Con- 
crete Construction.  2d  Ed.,  revised  and  enlarged.  439  pp.  164  figs. 
17  plates.  5H  X91A-  Cloth.  $3.50.  1909.  W,  CH. 

Warren,  F.  D. — .  Handbook  on  Reinforced  Concrete.  2d  Ed.,  revised. 
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Watson,  Wilbur  J. — .  General  Specifications  for  Concrete  Work;  as 
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1908.  Wilbur  J.  Watson,  Citizens'  Bldg.,  Cleveland,  O. 

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BIBLIOGRAPHY.  1315 

Concrete  Blocks. 

Rice,  H.  H. — ,  and  Torrance,  Wm.  M. — .  Concrete  Blocks:  Their  Manu- 
facture and  Use  in  Building  Construction.  122  pp.  Ill'd.  Demy  8vo. 
$1.50.  1907.  AC. 

Whipple,  Harry — .  Concrete  Stone  Manufacture.  255  pp.  Ill'd.  4  X7. 
Leather.  $1.00.  Concrete-Cement  Age  Publishing  Co.,  Detroit,  Mich. 

Cements,  Limes,  Plasters,  etc. 

Butler,  David  B. — .     Portland  Cement;    Its  Manufacture,  Testing  and  Use. 

2d  Ed.,  revised.      406  pp.      97  ills.     51A  X8%.     Cloth.     $5.00. 
*Eckel,  Edwin  C.— .     Cements,  Limes,  and  Plasters:    Their  Manufacture 

and   Properties.     746   pp.     165   figs.     254   tables.     8vo.     Cloth.     $6.00. 

1905.     W. 
*Falk,  Myron  S.— .     Cements,  Mortars   and    Concretes.    176   pp.    Tables, 

plates  and  figs.     6  X9.     Cloth.     $2.50.     1905.     MC. 
*Gillmore,  Q.  A. — .     Practical  Treatise  on  Limes,  Hydraulic  Cements  and 

Mortars.     334  pp.     56  ills.     8vo.     Cloth.     $4.00.     1905.     VN. 
*Jameson,  Charles  D.— .     Portland  Cement.     8vo.      Cloth.       $1.50.      VN. 
*Le  Chatelier,  H. — .     Experimental  Researches  on  the  Constitution  of  Hy- 
draulic Mortars.     Translated  by  J.  L.   Mack.      140  pp.     $2.00.     1907. 

McG. 
Redgrave,   Gilbert   R. — ,   and  Spackman,   Chas. — .     Calcareous  Cements. 

2d  Ed.     254  pp.     63  plates.     $4.50. 
Spalding,  Frederick  P.—.     Hydraulic  Cement.     310  pp.     34  figs.     12mo. 

Cloth.     $2.00.     1907.     W. 
Taylor,  W.  Purves— .     Practical  Cement  Testing.     330  pp.     142  ills.     58 

tables.     6X9.     Cloth.     $3.00.     1906.     MC. 

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INDEX. 


The   numbers   refer   to  the   pages;    those  in  parentheses,  to 
paragraphs. 

In  the  alphabetical  arrangement,  minor  words,  as  "and,"  "between," 
"  in,"  "  on,"  "  through,"  etc.,  are  neglected. 


See  also  table  of  Contents,  p  vi. 


Abrasion— Beam. 


A. 


Abrasion, 

of  mortar  and  concrete,  1136. 
Absorption, 

by  concrete,  1137,  1206  (39). 
Accelerated  tests  for  cements,  938, 

945. 

Acid,  in  mortar,  1135,  1136,  1138. 
Adhesion, 

of  concrete,  947  /  (36),  947  j  (67), 
1090   (39),   1106    (37),   1111, 
1126,    1128  (6),  1129  (9,  16), 
1139,    1196  (113,  etc), 
-unit,  1126. 

Aggregate,  Aggregates,  1084,  1136, 
1137,  1186.      See  also  the  kind 
in  question, 
analysis,  946. 
cinder—,  1084  (8),  1103  (1),  1137, 

1187  (12),  1197  (127). 
cyclopean—-,     1085,     1090     (40), 

1187  (15). 
effect  of —  on  weight  of  concrete, 

1103  (1). 

grading,  946,  1088,  1089. 
quartering,  946  (4). 
for  reinforced  concrete,  1110  (7). 
washing,  1091  (15). 
Alum, 

and  clay,  1135,  1171. 

and  soap,  for  waterproofing,  1105 

(20),  1137. 

Alumina,  in  cement,  930. 
Analysis, 

of  sand,  etc,  946. 

Anchor  plates,    in    reinforced    con- 
crete, 1129. 
Arch,  Arches, 

cpncrete — ,  cost,  1210  (60). 
Artificial 

stone,  concrete,  1084,  1193. 
Asphalt, 

waterproofing,  1105. 


B. 


Bag,  cement—,   935    (56),   940    (1). 

1186  (3,  4). 

Ballast.     See  Aggregate. 
Bar,     Bars.       See     Reinforcement, 

bars. 
Barrel, 

cement—,  935  (51),  940  (1),  1186 

(3). 
Beam,  Beams, 

axis,  neutral—,  1138. 
concrete — , 

C9ntinuous — ,  1126,  1127,  1200. 
diagonal  stresses  in — ,  1125. 
forms,  1096. 
max  stresses  in — ,  1125. 
reinforced—,  1115,  1198.       See 
also  Beams,  reinforced  con- 
crete. 

shear  in—,  1123. 
shear  reinforcement,  1124,  1126 

(55-57),  1128  (3). 
specifications,  1198. 
strength  of — ,1115.   • 
stresses  in — ,  1115,  1125. 
diagpnal — ,  1125. 
maximum — ,  1125. 
continuous — ,  494  g,  1126,   1127, 

1200. 
reinforced     concrete,     specfns, 

1200. 
deflections, 

reinforced   concrete — ,   specfns, 

1201  (186). 
diagonal  stresses  in — ,  494  a,  494  e, 

1125. 
floor — ,    1198.        See   also   under 

Floors. 

horizontal  shear  in — ,  494  c,  494  e. 
loads,  suddenly  applied — ,  461. 
maximum    stresses    in — ,    494    a, 

494  e. 
neutral  axis  in — ,  1138. 


INDEX. 


Beam— Cement. 


Beam,  Beams  —  continued. 

principal  stresses,*  494  c,  494  g. 
reinforced  concrete  —  ,  1115,  1198. 
adhesion,  1106  (37),  1111,  1126, 

1128     (6),     1129    (9,    16), 

1139,  1196. 
axis,  neutral  —  ,  1138. 
continuous—,  1126,  1127,  1200. 
cost,  1122  (20  d),  1210  (57,  58). 
deflections,  1201  (186). 
design,  1120. 

diagonal  stresses  in  —  ,  1125. 
double  reinforcement,  1127. 
forms  for—,  1096. 
investigation,  1119,  1123. 
maximum  stresses  in  —  ,  1125. 
moments  in—,  1116  (7),  1117, 

1118   (14,   17),   1121,   1122 

(23),  1122  (30),  1123,  1200. 
neutral  axis,  1138. 
ratio     of     steel     and     concrete 

areas,    1116    (5,    6),    1117, 

1118  (11,  12,  15,  16),  1121. 
shear  in  —  ,  1123. 
shear  reinforcement,  1124,  1126 

(55-57),  1128  (3). 
specfns,  1198. 
stirrups,  1124,   1128   (3),   1139. 

spacing,  1199  (162). 
stresses   in—,    1116    (8),    1117, 

1118    (13,    15,    16) 


1121, 
(32), 


,        ,          , 
1122    (21-23),    1123 
1125,  1127  (66). 
diag9nal  —  ,  1125. 
maximum  —  ,  1125. 
T-sections,  1122,  1199  (171). 
tension  in  upper  side,  1127. 
theory,  1115  (4). 
shear,  494  c,  494  e,  1123. 
strength,  strengths,  1115. 
stress,  stresses,  in  —  , 

diagonal—,  494  a,  494  e,  1125. 
maximum  —  ,  494  a,  494  e,  1125. 
principal  —  ,  494  c,  494  g. 
suddenly  loaded  —  ,  461. 
vertical  shear  in  —  ,  494  c,  494  e. 
Blocks, 

concrete  —  ,  1203,  1204. 
Boiling  tests  for  cement,  938,  945. 
Bond.     See  Adhesion. 
Brass, 

effect  of  mortar,  etc,  on  —  ,  1136. 
Brick,  Bricks, 

incrustations,  947  j  (69). 
-work, 

mortar  required   for  —  ,  947  d. 
Briquet,    Briquets,    cement  —  ,    941 

(4),  944  (10). 
Broken 

stone,  1084,  1085,  1088,  1137, 

1207  (10). 

for  concrete.     See  Aggregate. 
Building,  Buildings, 

concrete  —  ,  cost,  1210  (61-3). 


C. 


Calcium  chloride,  947  g  (45  c),  1107 

(56),  1135. 
Carbonic  acid, 

effect  on  concrete,  1138. 
Cement,    930-945,    1086    (8),    1135. 
For  strength,  setting,  etc,  per- 
taining   to    mortar,    see    under 
Mortar. 

accelerated  tests  for — ,  938,  945 
adulterants,  934  (39). 
age,  935  (60),  1135. 
analyses,  933  (32),  942  (4,  8). 
bags,  935  (56),  940  (1),   1186   (3. 

4). 
barrels,   935    (51),   940   (1),    1186 

(3). 

boiling  test  for — ,  938,  945. 
brand,  specfns,  1186  (1). 
brick-dust—,  931  (6). 
briquet,  941  (4),  944  (10). 
in  bulk,  935  (59). 
calcium  chloride,  947  a,  1107  (56), 

1135. 

cementation  index,  934  (38). 
chemical 

action  of — ,  1135. 
analysis,  933    (32),  942    (4,  8). 
tests,  936,  (64). 
chemistry,  933  (32). 
clay  in—,  930,  1135. 
color,  934. 

composition,  933  (32),  942  (4,  8). 
cost,  1207  (7). 
deterioration,  936  (60,  61). 
effects  of —  on — .       See  material 
or  agency  in  question,  under 
Cement, 
elements,  930  (2),  933   (32),  942 

(4,  8). 

Erz— ,  933  (30). 
experiments,  1135. 
exposure,  936  (60,  61),  947  h  (51), 

1135,  1186  (4). 
factor,  lime — ,  934  (37). 
fineness,    934,    940  (3),    941    (3), 

943  (6),  1135. 

flashing,  936  (63),  947  A  (51). 
grout,  1102  (128),  1105  (22). 
gypsum  in—,  947  g  (45  a),  947  h 

(55),  1135. 

hardening,  930,  947  /,  947  h,  947  t. 
hydraulic 

index,  933  (33). 
lime,  933  (31). 
modulus,  933  (35). 
index, 

cementation—,  934  (38). 
hydraulic—,  933  (33). 
ingredients,  930  (2),  933  (32),  942 

(4,  8). 

iron  ore—.  933  (30). 
lime  in—,  930,  942  (S).      See  also 

Lime. 

lime  factor,  934  (37). 
lime,  hydraulic—,  933  (31). 


INDEX. 


Cement— Concrete. 


Cement — continued. 

lime  sulphate  in — ,  947  g  (45  a), 

947  h  (55),  1135. 
loam  in — ,  1135. 
magnesia  in — ,  930   (4) ,  940   (3) , 

942  (8). 

manufacture,  931. 
mix,  typical — ,  1135. 
modulus,    hydraulic—,   933    (35). 
mortar.     See  Mortar, 
in  mortar,  947  d. 
natural — ,  1135. 

in  concrete,  1086, 1186, 1191  (56). 
uses,  932  (21),  1186  (1). 
needle,  Vicat— ,  947  g  (43). 
packages,  935  (50),  940  (1),  1186 

(3,  4). 
Portland—, 

manufacture,  931  (14). 
uses,  932  (21),  1186  (1). 
white — ,  933  (29). 
properties,  934,  940  (3).    See  also 

the  property  in  question. 
Puzzolan— ,  930  (4),  932. 
quantities     required     and     used, 

1086,  1135. 

requirements,  937,  940,  942. 
restoration,  936  (62). 
rock,  930  (4). 
Roman—,  931  (12). 
Rosendale— ,  931  (11). 
samples,  940,  942  (1). 
setting.       See    Concrete,    setting, 

and  Mortar,  setting, 
shipment,  935  (59),  940  (1),  1186 

(3). 

silica—,  932  (25),  1135. 
slag—,  930,  932  (22). 

water  required,  947  /  (38). 
soundness.     See  under  Mortar, 
specific  gravity,  934  (46),  940  (3), 

942. 
specifications,  937,  940,  942,  1184, 

1186. 

Am  Soc  Civ  Engrs,  942. 
Am  Soc  Testg  Materials,  940. 
Engng    Standds    Comm    of    Gt 

Brit,  940. 

U.  S.  Engr  Officers,  937. 
storage,  936  (60,  61),  947  h  (51), 

1186  (4). 

strength.     See  under  Mortar, 
sulfuric   acid   in—,   940    (3),   942 

(8),  1135. 

testing  machines  for — ,  938. 
tests,  936,  937,  940,  942,  947  i, 

1186  (2). 

typical  mix,  1135. 
Vicat  needle,  947  g  (43). 
weight,  934,  etc. 
white—,  933  (29). 

Cementation  index,  934  (38). 
Chloride,    calcium — ,    947    g,    1107 

(56),  1135. 
Cinder, 

concrete,  1084  (8),  1103  (1),  1137, 

1187  (12),  1197  (127). 


Clay 

and  alum,  1135,  1171. 
in  cement,  930,  1135. 
in  concrete,  1084  (11),  1135,  1186 

(6). 

in  mortar,  947 /,  1135. 
in  sand,  1135,  1186  (6). 
test  for—,  947  c  (32). 
Clearance, 

in  reinforced  concrete,  1196. 
Clinton, 

welded  wire,  1132. 
wire  lath,  1132. 

Clips,  for  cement  briquets,  941  -,  944. 
Closet,  moist — ,  945. 
Coefficient,  Coefficients.        See  also 

the  subject  in  question, 
expansion — , 

in  reinforced  concrete,  1110  (9), 

1138. 
safety.       See  the  construction  or 

material  in  question, 
uniformity — ,  947,  1135. 
Cold, 

effect  of—, 

on    concrete,    1094  (57),    1102 
(133),  1107  (44),  1138,  1191. 
-twisted  lug  bar,  1131  (22). 
-working  of  iron  and  steel,  1129 

(9). 
Column,  Columns, 

concrete—,      1112,     1113,     1138, 

1197. 

footings  for — ,  1114. 
forms,  1095  (64). 
hooped—,  1113, 1198  (144,  etc), 
reinforced — ,   1112.        See  Col- 
umns, reinforced  concrete, 
strength  of— ,  1138. 
eccentric  loading,  1198. 
footings,  1114. 

hooped—,  1113,  1198  (144,  etc), 
reinforced  concrete — ,  1112,  1134, 

1197. 

footings  for — ,  1114. 
forms,  1095. 
formula,      Rankine's — ,      1113 

(10). 

hooped—,  1113,  1198  (144). 
reinforcement,    1134,    1197    (131, 

etc). 

Concrete,  1084.     For  adhesion,  set- 
ting and  other  properties  per- 
taining to  mortar,  see  also  under 
Mortar,     cement — .     See     also 
under    structure    in    question. 
See  also  Reinforced  concrete, 
abrasion,  1136. 
absorption,  1137,  1206  (39). 
acids,  effect  of—,  1108  (69),  1138. 
adhesion,  947  /  (36),  947  j   (67), 
1090  (39),  1106  (37),  1111,  1126, 
1128  (6),  1129  (9,  11,  16),  1139, 
1196. 

age,  effect  of—,  947  i  (64),  1137. 
aggregates.     See  Aggregates, 
air,  effect  of—,  1138". 


Concrete,  alum— Concrete,  loads. 


Concrete — continued. 

alum  and  soap  treatment,  1105 
(20),  1137. 

arches,  cost,  1210  (60). 

asphalt,  for  waterproofing — ,  1105 
(25). 

beams.  See  Beams,  concrete — ; 
Beams,  reinfd  concrete — ; 
and  Floors. 

behavior,  1137. 

blocks, 

hollow — ,  for  buildings,  specfns, 

1204. 
practice,  1203. 

bond.     See  Concrete,  adhesion. 

broken  stone,  1084,  1085,  1088, 
1137,  1207  (10).  See  also 
under  Aggregate,  and  Stone. 

building  blocks,  specfns,  1204. 

buildings,  cost,  1210  (61-3). 

burning,  effect  of — ,  1108  (62,  63, 
65),  1138. 

carbonic  acid,  effect  of — ,  1138. 

cement  for—,  930,  1086  (8). 

chemical  effects,  1108. 

churning,  specfns,  1189. 

cinder—,  1084  (8),  1103  (1),  1137, 
1187  (12),  1197  (127). 

clay  in—,  930,  947  /,  1084  (11), 
1135,  1186  (6). 

coefficient, 

expansion—,  1110  (9),  1138. 

cold,  effect  of—,  1094  (57),  1102 
(133),  1107  (44),  1138,  1191. 
See  also  Concrete,  freezing. 

coloring,  1103,  (137). 

columns.  See  Columns,  con- 
crete— ;  and  Columns,  rein- 
forced concrete — . 

compacting,     1100,     1137,     1189, 

1190  (44). 
cost,  1210  (47,  48). 

compressive  strength,  1106  (32), 
1193  (81,84,85). 

conductivity,  thermal — ,  1138. 

consistency,  1090,  1094  (54),  1187 
(22). 

continuous  beams,  1126,  1127, 
1200. 

contraction,  947  h  (56). 

coping,  1192  (76). 

cost  of — ,  1207. 

cracks  in — ,  1108  (61). 

crusher  dust,  947  e  (25),  1186  (7). 

cyclopean—,  1085,  1090  (40), 
1187  (15). 

dehydration,  1108  (63). 

density,  1088,  1089,  1137. 

depositing.  See  Concrete,  plac- 
ing— . 

dry — .     See  also  Concrete,  consis- 
tency, 
cost,  1210  (54). 

ductility,  1111  (16),  1137. 

dumping,  1093  (52).  See  also 
Concrete,  placing — . 

durability,  1137. 


Concrete — continued. 

effect  of  air,  etc,  on — .     See  Con- 
crete, air,  etc. 

elastic  limit,  1138. 

elastic  modulus,  1106,  1110,  1111, 
1138,  1194. 

electrolysis,  1108  (68),  1138,  1139. 

elongation,  1111  (16). 

expanded  metal,  1132  (37). 

expansion,  947  h  (56),  1108,  1137, 
1110  (9),  1138. 

experiments,  1135. 

fatigue,  1138. 

finish,  1102,  1137,  1192. 
cost,  1210  (50-52). 

fire,  effect  of—,  1108  (62,  63,  65), 
1138,  1139. 

floors.     See   Floors,    and    Beams, 
reinforced  concrete — . 

flow  of—,  1137. 

forms.     See  Forms. 

foundations,  leveling,  1086  (5). 

freezing,    1094    (57),    1102    (133), 

1107  (44),  1138,  1191. 
calcium  chloride,  1107  (56). 
forms,  removal  of — ,  1191  (58). 
protection,  1107. 

friction,  1139. 

frost,  see  Concrete,  freezing, 
frozen — ,  removal  of — ,  1191  (55). 
gases,  effect  of —  on — ,  1108  (72). 
girders.     See    also    Floors,    con- 
crete— ;  Beams,  concrete — . 
forms,  1096. 
grading,  1089. 
gravel  for — .     See  Gravel, 
grouting,  1102  (128),  1105  (22). 
handling  and  mixing—,  1090. 
heat,  effect  of—,  1106  (40),  1107, 

1108  (62,  63,  65),  1138. 
impermeability,  1088   (22),  1103, 

1136,  1138,  1192,  1193  (78). 
ingredients.     See  also  under  ma- 
terial in  question, 
handling,  1090. 
heating,  1107  (53). 
measurement,   1091    (10),   1093 

(38),  1187  (21). 
required,  1087. 
storage,  1091  (5). 
inspection,  cost,  1210  (49). 
in  iron  cylinders,  expansion,  1108 

(60). 
joints  in—,  1099,  1105  (21),  1108 

(61),  1190. 
laitance,  947  /  (36),  947  k   (71), 

1137. 
large  stones  in—,  1085,  1090  (40), 

1187  (15). 

law  of  powers,  1138. 
layers,    1094    (53),   1190   (40,  43, 

44). 

for  leveling  foundations,  1086  (5). 
lifting—,  1092  (24). 
limit,  elastic—,  1138. 
loads,  allowable — ,  specfns,   1193 
(83). 


INDEX. 


Concrete,  loam— Concrete,  stress. 


Concrete — continued, 
loam  in—,  1084  (11). 
manipulation,  specfns,  1189.     See 
also  Concrete,  placing — ;  Con- 
crete,    mixing — ;     Concrete, 
handling — . 
and     masonry,    in    combination, 

1086  (7). 

mass—,  cost,  1210  (56). 
materials.      See    Concrete    ingre- 
dients. 

-metal.       See     Reinforced     con- 
crete, and  Reinforcement, 
metal  in — .     See  Reinforcement. 

corrosion.  1110  (5),  1136. 
mica  in— ,  1135,  1186  (6). 
mix,  natural — ,  1087. 
mixers,    1092,    1101    (125),    1208 
(27) .     See  also  Concrete  mix- 
ing. 

mixing,  1092,  1137,  1188. 
batch,  1188  (29). 
cost,  1208. 

hand—,  1188  (28,  30). 
machine—,  1092  (32),  1188  (28). 

See  also  Concrete  mixers, 
measurement,  1187  (21). 
mixers.     See  Concrete  mixers, 
for  sidewalks,  1202. 
water,  1090,  1136,  1187. 
weather,  effect  of — ,  1092  (30). 
wind,  1092  (30). 
modulus, 

elastic—,     1106,     1110,     1111, 

1138,  1194. 
rupture — ,  1106  (38). 
moistening,  1190  (38),  1191. 
molded—,  1204. 
molds  for — .     See  Forms, 
mortar  for — .     See  Mortar, 
natural  cement — ,  1086. 
freezing,  1191  (56). 
uses,  1086,  1186. 
natural  mix,  1087. 
night  work,  specfns,  1189  (37). 
oil,  effect  of—,  1108   (71),   1138. 
painting,  1103  (138),  1137. 
paving,  1201. 

percolation.     See   Concrete,    per- 
meability, 
permeability,     1088,     1103,     1136, 

1138,  1177,  1192,  1193  (78). 
permit,  specfns,  1196. 
picking,  1102  (129). 
in  piles,  1101  (124). 
placing,    1093,    1137,    1189.     See 

also  Concrete,  handling, 
cost,  1208,  1209. 
for  sidewalks,  specfns,  1202. 
underwater,  1100,  1190. 

in  bags,  1101   (119). 
plain — ,  1086.     See  also  other  sub- 
heads of  concrete, 
plants,  1090  (1),  1101   (125). 
plastering,  1102  (127),  1192  (66), 

1193  (79). 
plasticity,  1137. 


Concrete — continued. 

plums  in—,  1085,  1090  (40),  1187 

(15). 

Potenzgesetz,  1138. 
powers,  law  of — ,  1138. 
practice,  1135. 
pressure,  effect  of — ,  1138. 
proportions,  1086,  1089. 
measurement,  1187   (21). 
in  reinforced   work,   1087    (13). 
protection,  1107. 

for  sidewalks,  1202,  1203. 
rain,  1191. 
rammers,  1189  (37). 
ramming,  1100,  1137,  1189,  1190 

(44). 

cost,  1210  (47,48). 
rehandling,  specfns,  1189  (37). 
rehydration,  1108  (64). 
reinforced — .   See  Reinforced  con- 
crete, and  Reinforcement, 
requirements,  1193. 
resistance  to  fire,  1108  (62,  63,  65), 

1138. 

retaining  walls,  cost,  1210  (59). 
re-tempering,  1137,  1189  (37). 
salt  in—,    1107    (55),    1108    (67, 

70). 

sand.     See  Sand, 
sea    water,    effect    of—,    947    k, 

1108  (67),  1136,  1138. 
setting,    1090    (39),    1106,    1137. 

See  also  Mortar,  setting, 
sewage,  effect  of—  on—,  1138. 
shear  in — ,  1123. 
shearing  strength,  1106  (36),  1138, 

1173,  1193  (82). 
shrinkage,  947  h  (56),  1137. 
sidewalks,  specfns,  1201. 
soap   and   alum   treatment,    1105 


1137.     See  also  Sound- 


sou 


(20),  1137. 
ndness, 


specifications,  1184,  1186. 
spreading,  cost,  1210  (47). 
steam,  effect  of — ,  1138. 
-steel.     See   Reinforced    concrete, 
steel   for    and    in — .     See    Rein- 
forced   concrete;     Reinforce- 
ment, 
stirrups,    1124,    1128    (3),    1139, 

1199  (162). 

stone    for—,    1084,    1085,    1088, 
1137,    1207    (10).     See    also 
under  Aggregate  and  Stone, 
storage,  cost,  1208. 
strength,  1106,  1137,  1138,    1193 

(81,  84,  85). 
compressive — ,  1106   (32),  1193 

(81,  84,  85). 
required,  1193. 
shearing—,     1106     (36),     1138, 

1173,  1193  (82). 
tensile—,  1106  (31,  36),  1138. 
torsional — ,  1173. 
transverse — ,  1106  (38). 
stress  and  stretch,  1138. 


INDEX. 


Concrete,  stresses— Form. 


Concrete — continued , 
stresses, 

allowable—,  1193  (83). 
stretch,  1111  (16). 
subaqueous,  1100- 
sunshine,  effect  of — ,  1138. 
superintendence,  cost,  1210  (49). 
surface  finish,  1102,  1137,  1192. 
Sylvester  process,  1105  (20),  1137. 
temperature,    effect    of — ,     1094 
(57),  1106  (40),  1107  (44),  1108 
(62,  63,  65),  1138. 
tensile   strength,    1108    (31,    36), 

1138. 

tests,  1109,  1200. 
thawing,  1107  (46,  47). 
thermal  conductivity,  1138. 
tooling,  1102  (129). 
torsional  strength,  1173. 
transportation,  cost,  1208. 
transverse  strength,  1106  (38). 
tremie,  1100  (116). 
voids  in— ,  1088,  1137 
volume  of  mortar,  1137. 
excess  required,  1088. 
walls, 

forms  for — ,  1096  (68). 
retaining — ,  cost,  1210  (59). 
washing,    cost,    1208    (18),    1210 

(51). 

in  water,  947  A;,  1100,  1190. 
water, 

effect  of— ,  1138. 

mixing—,  1090,  1136,  1187. 

salt—,  1108  (67). 

sea—,  947  k,  1108  (67),  1136, 

1138. 

waterproofing,    1104,    1192,    1193 
(78).    See  also  Concrete,  per- 
meability, 
watertightness.         See    Concrete, 

permeability, 
weather,  1191. 
weight,  1103  (1). 
wet — ,  cost,  1210  (54). 
wetness.       See   Concrete,   consis- 
tency. 
Conductivity, 

thermal—,  1138,  1139. 
Considere, 

hopped  columns,  1113  (15). 
Consistency.     See    under    Concrete 

and  Mortar. 

normal—,  943  (7),  947  g  (43). 
Continuous  beams,  494  g,  1126, 1127, 

1200. 

Coping,  1192. 
Copper, 

effect    of    cement,    mortar,    etc, 

on—,  1136. 
Corrugated 

bars,  1131  (24). 
Crusher,  Crushers, 

dust,  947  e  (25),  1186  (7). 
Cup  bars,  1131  (25). 
Cyclopean  concrete,  1085,  1090  (40), 
1187  (15). 


Cylinder,  Cylinders, 

iron — ,  concrete  in — ,  1108  (60). 

D. 

Deformed  bars,  1110  (6),  1129  (15, 

16),  1139,  1194. 

Depositing.     See  Concrete,  placing. 
Dehydration,    1108    (63). 
Diagonal  stresses  in  beams,  494  a, 

494  e,  1125. 

Diamond  bar,  1131  (26). 
Double  reinforcement,   1127,   1199 

(165-6). 
Dumping  concrete.     See  Concrete, 

placing. 
Dust, 

crusher—,  947  e  (25),  1186  (7). 

E. 

Economy  unit  frame,  1133. 
Effective  size,  947. 
Efflorescence,  947  j  (69). 
Electrolysis,  1108  (68),  1138,  1139. 
Erz-cement,  933  (30). 
Evaporation,  from  mortar,  1136. 
Expanded  metal,  1132  (37). 
Expansion  of  concrete,  947  h  (56), 

1108, 1137. 
Experiments,  1135,  1140. 

F. 

Factor, 

lime—,  934  (37). 

safety — .       See  the  construction 

or  material  in  question. 
Feret,  R. — ,  sand  analysis,  947. 
Fineness.     See  Cement,  Sand,  etc. 
Fire,  Fires, 

effect  on  concrete,  1108  (62,  63, 

65),  1138. 
-proof  work, 

reinforced  concrete  in — ,    1196 

(120). 
Flashing,  of  cement,  936  (63),  947  h 

(51). 
Floor,  Floors, 

forms,  1096  (67),  1098   (93). 
reinforced—,  1198. 
Footings, 

for  columns.     See  Columns. 
Form,  Forms. 

for  concrete,  1094,  1137,  1189. 
adhesion,  1099. 
beams,  1096. 
for  blocks,  1203  (3). 
columns,  1095. 
cost,  1209. 

depreciation,  1209  (42). 
floors,  1096. 
for  girders,  1096. 
lagging,  1096,  1189  (34). 
lumber  for — ,  1097. 
reinforced — ,  1095. 
removal,    1099,    1191    (58,  61). 
shifting,  cost,  1209  (42). 


INDEX. 


Form-Mix. 


Form,  Forms — continued, 
sidewalks,  1202. 
slabs,  1096. 
strength,  1098. 
tie-rods  in— ,  1189   (36). 
walls,  1096  (68). 
Wiederholt  system,  1096  (69). 
Foundation, 

leveling —  by  concrete,  1086  (5). 
Frame, 

unit—,  1133. 
Freezing, 

concrete.     See  Concrete,  freezing. 
Frost, 

in  concrete.      See  Concrete,  freez- 
ing, 
forms,   removal  of — ,   1191    (58). 


G. 

Grading, 

aggregate,  1088,  1089. 

sand, 946. 
Granite, 

as  aggregate,  1137. 
Granulometric  analysis  of  sand,  946. 
Gravel, 

as  aggregate,  1136,  1137. 

in  concrete,  1084,  1136,  1137. 

-concrete,  cost,  1210  (55). 

cost,  1207  (9). 

effective  size,  947. 

quartering,  946  (4). 

screenings,   947  /   (26),   946    (3), 
1137. 

uniformity  coefficient,  947. 
Grout,  1102  (128),  1105  (22). 
Gvpsum,  947  g  (45  a),  947  h  (55), 
1135. 

H. 

Hardening,  930,  947  /,  947  h,  947  i. 
Havemeyer  bar,  1131  (27). 
Heat, 

effect    on    concrete,     1107     (44), 

1108  (62,  63,  65),  1138. 
Hooped  columns,   1113,  1198    (144, 

etc). 
Horizontal 

shear,  494  c,  494  e. 
Hydraulic 

index,  933  (33). 

lime,  933  (31). 

modulus,  933  (35). 


I. 

Incrustation 

of  walls,  947  j. 
Index, 

cementation — ,  934  (38). 

hydraulic—,  933  (33). 
Iron, 

cement,  mortar,  etc,  effect   of- 
on— ,  1110,  1136,  1139. 

-ore  cement,  933  (30). 

C14 


J. 


Joint,  joints,  in  concrete  work,  1099, 
1105  (21),  1108  (61),  1190. 

K. 

Kami  trussed  bar,  1133. 


L. 


for  forms,  1096,  1189  (34). 
Laitance,   947  /   (36),   947  k   (71), 

1137. 
Lath, 

rib—,  1133. 

wire—,  1132. 
Lead, 

effect    of    cement,    mortar,    etc, 

on—,  1136. 
Lime, 

in  cement,  930,  942  (8). 

factor,  934  (37). 

hydraulic—,  933  (31). 

in  mortar,  947  e,  947 /,  1135,  1136. 

quick —    and    slack — ,    931     (7), 
947  e  (11,  12). 

stone.     See  Limestone. 

sulphate,  947  g  (45  a),  947 ft  (55), 

1135. 
Limestone, 

as  aggregate,  1137. 

in  cement  manufacture,  930  (4). 

crushed —  vs  sand,  1135. 

screenings,  947  /  (26). 
Loam, 

in  cement,  1135. 

in  concrete,  1084  (11). 

in  sand,  1135,  1186  (6). 
test  for—,  947  c  (32). 
Lug  bar,  1131  (22). 


M. 

Magnesia, 

in  cement,  930  (4),  940  (3),  942 

(8). 

in  mortar,  947  e  (14). 
Masonry 

and  concrete  in  combination,  1086 

(7). 

incrustation  of — ,  947  j. 
mortar  required  for — ,  947  d. 
pointing,  947  j  (70). 
Maximum  stresses  in  beams,  494  a, 

494  e. 
Mechanical    analysis    of    sand,    etc, 

946. 

Melan  system,  1133. 
Metal,  metals, 

effect  of  cement,  etc,  on — ,  1110 

(5),  1136,  1139. 
expanded—,  1132  (37). 
rib—,  1132  (41). 
Mica,  in  mortar,  1135,  1186  (6). 
Mix,  natural—,  1087. 


IND^X. 


Mixers— Mortar. 


Mixers,     concrete—,      1092,      1101 

(125),  1208  (27). 
Mixing, 

concrete,  1092,  1137,   1188.     See 

also  Concrete,  mixing. 
Modulus, 

hydraulic—,  933  (35). 
Moist  closet,  945. 
Moisture, 

in  sand,  947  b,  1135,  1186  (6). 
Molded  concrete,  1204. 
Molds.     See  Forms. 
Moments, 

in   continuous  beams,  494  g. 
in  reinfd  beams,  1116  (7),  1117, 
1118  (14,   17),  1121,  1122   (23, 
30),  1123,  1200. 
Monier  system,  1132  (36). 
Monolith  bar,  1131  (29). 
Mortar, 

abrasion,  1136. 
absorption,  1137,  1206  (39). 
accelerated  tests  for — ,  938,  945. 
acid  in—,  1135,  1136. 
adhesion,  947  /  (36),  947  j  (67), 
1090    (39),    1106    (37),    1111, 
1126,   1128   (6),   1129   (9,    16), 
1139,  1196. 
aeration,  1136. 
age,  947  t  (64),  1137. 
boiling  test  for—,  938,  945. 
briquet,  941   (4),  944  (10). 
calcium  chloride  in — ,  947  g,  1107 

(56),  1135. 

cement—,  930,  947  d,  1136. 
cement  in — ,  947  d. 
chemistry  of — ,  947  d  (2). 
clay  in—,  947 /,  1135. 
consistency,  947 /,  1136. 

effect  on  adhesion,  947  /  (36). 
laitance,  effect  of—  on—,  947  / 

(36). 

normal—,  943  (7),  947  g  (43). 
contraction  of — ,947  h  (56),  1137. 
crusher  dust  in—,  947  e  (25),  1186 

(7). 

density  of—,  1136. 
drying,  1108  (59). 
efflorescence,  947  j  (69). 
evaporation  from — ,  ll36. 
expansion  of—,  947  h  (56)    1108, 

1136, 1137. 
experiments,  1136. 
finish,  947  j,  1102,  1137,  1192. 
freezing.     See  Concrete,  freezing, 
grading,  1136. 
gypsum  in — ,  947  g  (45  a),  947  h 

(55),  1135. 

hardening,  930,  947  /,  947  h,  947  i. 
incrustation,  947  j  (69). 
laitance,  947  /  (36),  947  k  (71), 

1137. 

lime  in—,  947  e,  947 /,  1135,  1136. 
magnesia  in — ,  947  e  (14). 
metals,  protection,  1110  (5),  1136, 

1139. 
mica  in— ,  1135,  1186  (6). 


Mortar — continued 
mixing,  944. 

mixing  water,  938,  943,  947  /. 
neat —  and  sand — ,  1136. 
needle,  Vicat—,  947  g  (43). 
normal  consistency,  943  (7),  9470 

(43). 

permeability,     1088     (22),     1103, 
1136,  1138,  1192,  1193  (78). 
for  plastering,  1136. 
plasticity,  1136,  1137. 
properties,  947  h. 
proportion  of —  in  concrete,  1136. 
proportions,  1136. 
quantity  required,  947  d. 
regrinding — ,  1137. 
retempering — ,  1137. 
richness,  1136. 
sal  ammoniac  in — ,  1136. 
salt  in—,  1107  (55),  1135,  1136. 
sand—  and  neat—,  1136. 
sand  in—,  946,  947  e,  947  j  (65), 

1135.   See  also  under  Sand. 
sea  water  in—,  947  k  (72). 
in  sea  water,  1136,  1138. 
setting,  940  (3),  942  (5),  943  (8), 

947 /,  1090  (39),  1137- 
acceleration,  947  o  (45). 
calcium    chloride,    effect    of — 

on— ,9470  (45  c). 
expansion  during — ,  1137. 
freezing,  effect  on — ,  1107  (45). 
gypsum,  effect  of —  on — ,  947  g 

(45  a). 

initial —  and  final — ,  947  g. 
lime,   effect   of —  on — ,   947   e. 
rate  of — ,  1137. 
retardation,  947  g  (45). 
sand,  effect  of —  on — ,  947   g 

(45). 
silica,  effect  of —  on — ,  947  g 

(45). 

speed,  947  g. 
temperature   as   affected   by — , 

947  g  (46). 

sewage,    effect    of —    on — ,    1138. 
shrinkage  of—,  947  e  (21),  947  h 

(56),  1137. 

slag  cement—,  947  /  (38). 
soundness,  937,  938,  940  (3),  942 
(6),  945  (16), 947 e  (13),  947  h 
(53),  1136,  1137. 
lime,   effect  of —   on — ,   947    e 

(13). 

strength,    940    (3),   941    (4),    945 
(15),  947  /  (34),  947  h  (52), 
947  i,  947  j,  1136. 
age,  effect  of —  on — ,  947  i  (64). 
compressive — ,  947  j  (66). 
consistency,    effect    of —   on — , 

947  /  (34). 
sand,   effect   of —  on — ,   947   j 

(65). 

shearing— ,  947  /  (66). 
sulphuric   acid  in — ,    1135,    1136. 
tests,  937,  940,  942,  947  i  (61). 
Vicat  needle,  947  g  (43). 


INDEX. 


Mortar— Reinforced. 


Mortar — continued, 
in  water,  947  fc,  1136. 
water,   mixing—,   938,   943,   947  /, 

1136. 

salt  in—,  1136. 
Mushroom  system,  1134  (51). 

N. 

Natural 

cement.     See  under  Cement. 

mix,  1087. 

Needle,  Vicat— ,  947  g  (43). 
Normal   consistency,   943    (7),  947  g 

(43). 

o. 

Oil, 

effect  of—  on  concrete,  1108  (71), 
1138. 

P. 

Painting,    on    concrete,    1103    (138), 
1137. 

Paving,  concrete  sidewalks,  1201. 

Permeability.     See  under  Concrete. 

Piles,  concrete  in— ,  1101  (124). 

Placing.     See  Concrete,  placing. 

Plaster  of  Paris,  947  a  (45  a),  947  h 

(55),  1135.     See  also  Gypsum, 
effect  of —  on  metals,  1136. 

Plastering, 

mortar  for — ,  1136. 

Plums    (cvclopoan    concrete),    1085, 
1090(40),  1187  (15). 

Pointing,  947  j  (70). 

Portland    cement.     See    under    Ce- 
ment. 

Pozzuolano,  930  (4),  932. 

Preservation  of  metals,  1136. 

Priddle  internal-bond  bar,  1131  (28). 

Principal  stresses,  494  c,  494  g. 

Protection  of  metals,  1136. 

Puzzolano,  930  (4),  932. 


O. 

Quartering  of  sand,  gravel  etc,   946 

(4). 
Quartz, 

as  aggregate,  1137. 

weight,  947  o  (19). 
Quick  lime,  931  (7),  947  e  (12). 


R. 

Ramming,  1100,  1137,  1189,  1190. 
cost  of—,  1210  (47,48). 

Rankine  column  formula,  1113  (10). 

Ransome  bar,  1130  (21). 

Rehydration,  1108  (64). 

Reinforced  concrete,  1110,  1139. 
See  also  under  the  structure  in 
question,  and  name  of  type  of 
reinforcement  in  question.  See 
also  Reinforcement. 


Reinforced  concrete — continued. 

adhesion,  1106   (37),  1111,  1126, 
1128    (6),    1129    (9,    15,    16), 
1139,  1196   (113,  etc), 
-unit,  1126. 

aggregate  for — ,  1110  (7).  See 
also  under  Aggregate. 

anchor  plates,  1129. 

bars.     See    Reinforcement,    bars. 

beams.  See  Beams,  reinforced 
concrete — . 

clearance,  1196. 

coefficient,  expansion — ,  1110  (9), 
1138. 

columns,  1112,  1134,  1197.  See 
also  Columns,  reinforced  con- 
crete— . 

conductivity,  thermal — ,  1138, 
1139. 

continuous  beams, 1126, 1127, 1200. 

contraction,  1110. 

cost,  1210  (57-8). 

elastic  modulus,  1110,  1195  (106). 
ratio,  n,  of—,  1111   (14),  1195 
(107),  1198  (153). 

electrolysis,  1108  (68),  1138, 1139. 

elongation,  1111  (16). 

expansion,  1110,  1138. 

.experiments,  1139. 

fire,  effect  of—  on — ,  1108  (62, 
63,  65),  1138,  1139. 

in  fireproof  work,  1196  (120). 

forms,  1095,  etc.     See  also  Forms. 

friction,    1111    (18),   1139. 

floors,  1096  (67),  1098  (93),  1198. 
forms  for—,  1098  (93). 

initial  stresses  in—,   1199    (159). 

methods  of  reinforcement,   1127. 

moments    in—,    1116    (7),    1117, 
1118  (14,  17),  1121,  1122,  1123. 

permit,  1196. 

pillars.  See  Columns,  reinforced 
concrete1 — . 

proportions,  1087  (13). 

reinforcement.  See  Reinforce- 
ment. See  also  name  of  type 
in  question. 

shear,  1123,  1139. 

shearing  stress,  permissible,  1199 
(161). 

shrinkage  stress,  1199  (159). 

slabs,  1122,  1123,  1128  (5),  1199 
(167),  1200,  1201. 

steel  in—,  1110  (5,  6),  1139. 
corrosion,  1110  (5),  1139. 

stirrups,  1124,  1128  (3),  1139, 
1199  (162). 

strength,  1110-1123. 

stresses  in—,  1116  (8),  1117,  1118 
(13,15,16),  1121,  1122  (21- 
23),  1123  (32),  1125,  1127 
(66),  1139,  1198,  1199. 

stretch,  1111  (16). 

tests,  1200. 

thermal  conductivity,  1138,  1139. 

thermal  stresses  in — ,  1199  (159). 

unit  adhesion,  1126. 


INDEX. 


Reinforcement— Sand. 


Reinforcement,     1127,     etc,     1139, 

1194.     See  also  name  of  type 

in  question. 

adhesion,  1106   (37),  1111,  1126, 
1128  (6),    1129    (9,    15,    16), 
1139,  1196  (113,  etc), 
bars,  1110,  1128-1131,  1139,  1194. 

corrugated — ,  1131   (24). 

cup—,  1131  (25). 

deformed—,  1110  (6),  1129  (15, 
16),  1139,  1194. 

diamond—,  1131  (26). 

lug—,  1131  (22). 

plain—,  1129  (10),  1139. 

supports  for — ,  1131. 

trussed—,  1133. 
clearance,  1196. 
in  columns,  1112,  1134,  1197  (130, 

etc). 

conductivity,  thermal — ,  1139. 
corrosion  of — ,  1139. 
cost,  1207  (11). 
disturbance  of—,  1139. 
double—,  1127,  1199  (165-6). 
electrolysis,  1139. 
expanded  metal,  1132  (37). 
friction,  1111  (18),  1139. 
lapping,  1196  (116). 
lath,  rib—,  1133. 
length,  1196  (116). 
metal,  expanded—,  1132  (37). 
metal,  rib—,  1132  (41). 
methods  of—,  1110,  1127,   1139, 

1194,  1199. 

mushroom  system,  1134  (51). 
percentage  of—,  1139,  1207  (12). 
placing,  cost,  1209  (45). 
proportions,  1139,  1207  (12). 
protection,  1196  (117). 
rib  lath,  1133. 
rib  metal,  1132  (41). 
rods,  supports  for — ,  1131. 
shapes,  structural — ,    1133. 
shear—,  1124,  1126  (55-57),  1128 

(3),  1139. 

steel  for—,  1139,  1195  (100,  etc), 
stirrups,  1124,  1128  (3),  1139. 

spacing  of — ,  1199  (162). 
strength  of—,  1139. 


max —  allowed,  1195. 

structural  shapes,  1133. 

supports  for — ,  1131. 

tension —  in  top  of  beam,   1127, 
1199  (165-S). 

thermal  conductivity,  1139. 

trussed—,  1128  (2),  1133. 

types  of—,  1110,  1127,  1139, 1194, 
1199. 

web—,   1132,   1199    (164). 

welded  wire,  1132  (40). 

wire  lath,  1132. 
Retaining  walls, 

cost,  1210  (59). 
Rib  lath,  1133. 
Rib  metal,  1132  (41). 


Rod,  rods, 

for     reinforced     concrete,     1110, 

1128, etc,  1131,  1139,  1194. 
Roman  cement,  931  (12). 
Rosendale  cement,  931  (11). 

Safety 

factor.     See  the  material  or  con- 
struction in  question. 
Sal  ammoniac,  in  mortar,  1136. 
Salt, 

in  concrete,  1107  (55),  1108  (67, 

70). 

in  mortar,  1107  (55),  1135,  1136. 
in  water  for  mortar,  1136. 
Sand, 

analysis,  946. 
in  cement  mortar,  947  e. 
character  of — ,  effect  of — ,  1135. 
clay  in—,  1135,  1186  (6). 

test  for—,  947  c  (32). 
coefficient,      uniformity — .      947, 

1135. 

compacting,  1135. 
composition,  946. 
in  concrete,  947  e. 
for  concrete  sidewalks,  specfns, 

1201  (2). 
cost,  1207  (8). 
vs  crushed  limestone,  1135. 
definition,  946  (1). 
density,  947  a,  1135. 

moisture,     effect     of — ,     on — , 

947  b. 
dirt  in—,  947  c,  1186   (6). 

strength  of  mortar,  947  e  (23), 

1135. 

effective  size,  947. 
fineness,  947  e  (18),  1135. 

shrinkage  of  mortar,  947  e  (21), 

947/i  (58). 
foreign  matter  in — ,  947  e   (23), 

1135,  1186  (6). 
friction  of — ,  1135. 
fusing  point,  1135. 
grading  of — ,  1135. 
grains, 

shape  of—,  947  b,  1135, 
size,  946,  947  6,  1186  (6). 
granulometric  analysis,  946. 
impurities  in — ,  947  e  (23),  1135, 

1186  (6). 

vs  limestone,  crushed — ,  1135. 
loam  in—,   1135,   1186   (6). 

test  for—,  947  c  (32). 
mechanical  analysis,  946. 
mica  in—,  1135,  1186  (6). 
moisture  in—,  947  6,  1135,  1186 

(6). 
in  mortar,  946,  947  e,  1135.      See 

also  Mortar, 
properties,  946,  947  c.     See  also 

Property  in    question,  under 
arid. 

proportion  of — ,  in  mortar,  947  d 
(4). 


INDEX. 


Sand— Tangential. 


Sand — continued. 

quantities  required  in  mortar,  947 

d  (4). 

quartering,  946  (4).      . 
vs  screenings,  947  e   (24),  947  / 

(27),  1135,  1186  (7). 
shape  of  grain,  947  b,  1135. 
sharpness,  947  e  (22),  947  c,  1186 

(5). 

silt  in—,  947  c  (32). 
size,  effective — ,  947. 
size  of  grain,  946,  947  b,  1186  (6). 
specific  gravity,  947  a   (19). 
specifications,  1186. 
standard—,  944  (9). 
-stone 

as  aggregate,  1137. 
storage,  1186  (6). 
strength  of  mortar,  947  j  (65). 
uniformity  coefficient,  947,  1135. 
voids  in — ,  947  a,  1135. 
washing,  947  c  (34). 
weight,  947  a   (19),  947  e. 
Screening,  Screenings,  946  (3),  1208 

gravel—,  947  /  (26),  946  (3),  1137. 

vs  sand,  947  e   (24),  947  /  (27), 
1135,  1186  (7). 

stone— ,947  /  (27),  1137. 
Sea  water 

effect   on   concrete,   947   k,    1108 
(67),  1136,  1138. 

in  mortar,  947  k  (72). 
Set,  456,  459. 

permanent — ,  456,  459. 
Setting.     See  Mortar,  and  Concrete. 
Sewage,  effect  on  concrete,    1138. 
Shale,  as  aggregate,  1137. 
Shapes,  structural — , 

for  reinfmt,  1133. 
Shear, 

in  concrete  beams,  1123. 

horizontal — ,  494  c,  494  e. 

in  reinforced  concrete  beams,  1 123. 

reinfmt,  1124,  1126  (55-7),  1128 
-     (3). 

unit—,  494  e. 

in  reinfd  cone  beams,  1125. 

vertical — ,  494  c,  494  e. 
Shearing, 

stress,  454. 

Sidewalks,  concrete — ,  1201. 
Silica  cement,  932  (25). 
Size,  effective — ,  947. 
Slabs,    reinfd    cone—,    1122,    1123, 

1128,  1199  (167),  1200,  1201. 
Slacking,  931. 
Slag  cement,  930,  932. 
Slaking,  931. 
Soap  and  alum  process,  1105  (20), 

1137. 

Soundness,  937,  938,  940   (3),  942 
(6),  945,  947  e  (13),  947  h,  1136, 
1137. 
Specific  gravity, 

test,  LeChatelier  method,  942. 


Specifications 

for  cement,  937,  940,  942. 
for  concrete,   1184,  1186. 
blocks,  1204. 
sidewalks,  1201. 

Steam,  effect  on  concrete,  1138. 
Steel, 

bending  tests,  1195  (109). 
in  concrete.     See  Reinforced  con- 
crete, steel    in — ,  and  Rein- 
forcement. 

elastic  modulus,  1110  (11). 
in  reinforced  concrete.       See  Re- 
inforced concrete,  steel  in — , 
and  Reinforcement,  steel — . 
structural — ,  elastic  modulus,  460. 
Stirrups,  1124,  1128   (3),  1139. 
spacing,  1199  (162). 
supporting    reinforcement,     1131 

(31). 

Stone,  stones, 
artificial—,  1193. 
broken—,  1137. 

voids,  in—,   1085,   1088. 
cost,  1207  (10). 
large — ,   in   concrete,    1085,    1090 

(40),  1187  (15). 
screenings,  947  /  (27),  1137. 
work,  mortar  required  for — ,  947  d. 
Strength,  454.     See  also  under  Con- 
crete, Mortar,  and  Reinfd  cone. 
Stress,  Stresses, 
components,  454. 
compressive — ,  454. 
diagonal — ,  in  beams,  494  a,  494  e, 

1125. 
maximum — ,    in    beams,    494    a, 

494  e. 

principal—,  494  r,  494  g. 
in     reinforced     concrete     beams, 

1115-1123,  1125,  1127  (66). 
shearing — ,  454. 
tensile — ,  454. 
torsional — ,  454. 
transverse — ,  455. 
ultimate — ,  456. 
unit — ,  456,  458. 

actual  and  nominal — ,  456. 
Stretch,  454,  455,  459. 

unit — ,  458. 
Structural  shapes, 

for  reinfmt,  1133. 
Suddenly   applied   loads,   461. 
Sulphuric  acid,  in  mortar,  1135, 1136. 
Sulphate,  lime—,  947  g  (45  a),  947  h 

(55),  1135. 

Sunshine,  effect  on  concrete,   1138. 
Sylvester  process,  1105   (20),  1137. 


T. 

T-beams,  1122,  1199  (171). 
Tamping, 

concrete,   1100,  1137,  1189,  1190, 

1210  (47,  48). 
Tangential  stress,  454. 


INDEX. 


Tensile— Zinc. 


Tensile 

strength,  454. 

stress,  454. 
Tension,  454. 
Test,  Tests, 

of    cement,   936,   937,   940,   942, 
947  i  (61,  62),  1186  (2). 

of  concrete,  1109,  1200. 
Testing  machine  for  cements,  938. 
Thacher  bar,  1131  (23). 
Thermal  conductivity,   1138,   1139. 
Tie-rods,  in  forms,  1189  (36). 
Torsion,  454. 
Tremie,  1100  (116). 
True  elastic  limit,  459. 
Truss  reinforcement,  1128  (2),  1133. 
Trussed 

bar,  1133. 

reinforcement,  1128  (2),  1133. 
Turner,  C.  A.  P.—, 

mushroom  system,  1134  (51). 

U. 

Ultimate  stress,  456. 

Uniformity  coefficient,  947,  1135. 

Unit,  Units, 

adhesion—,  1126. 

frame,  1133. 

shear,  494  e. 

in  reinfd  cone  beams,  1125. 

V. 

Vertical 

shear,  494  c,  494  e. 
Vicat  needle,  947  g  (43). 
Voids, 

in  broken  stone,  1088. 

in  concrete,  1088,  1137. 

in  sand,  947  a,  1135. 


Volume, 

constancy  of —  (soundness),  937, 
938,  940  (3),  942  (6),  945  (16), 
947  e  (13),  947  h,  1136,  1137. 


W. 

Wall,  Walls, 

concrete—,  forms,  1096  (68). 
retaining — ,  concrete — , 

cost,  1210  (59). 
Washing  concrete,  cost,  1208   (18), 

1210  (51). 
Water, 
sea — , 
effect  on 

concrete,  947  k,    1108    (67), 

1136,  1138. 
mortar,  947  k  (72). 
Web     reinforcement,     1132,     1199 

(164). 

Welded  wire,  1132  (40). 
White 

efflorescence  on  walls,  947  j. 
"  Portland  cement,  933  (29). 
Wire, 

lath,  1132. 
welded—,  1132  (40). 


Y. 

Yield  point,  455,  460. 

Z. 

Zinc,  effect  of  cement  mortar  on — , 
1136. 


THE   END. 


YB  51896 


